Art. XXXI.—On the New Zealand Desmidieæ. Additions to Catalogue and Notes on various Species.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 15, 1882, Unnumbered Page

Art. XXXI.—On the New Zealand Desmidieæ. Additions to Catalogue and Notes on various Species. By W. M. Maskell, F.R.M.S. [Read before the Philosophical Institute of Canterbury, 5th Ootober, 1882.] Plates XXIV. and XXV. The following paper consists of two parts :—First, a list, with descriptions and figures, of those plants which I have been able to add to my former catalogue; and secondly, notes upon some of the species described or mentioned in my paper, vol. XIII. of the Transactions, 1880, p. 297. Several of the plants given in the following list have come to me in gatherings from Hawke's Bay, and I must express my thanks to Dr. Spencer, of Napier, who has kindly forwarded these gatherings, and in other ways materially assisted me. Indeed, strictly speaking, I have no right to include these in my paper: but Dr. Spencer informs me that he is not able this year to publish them. I understand that he proposes shortly to describe several new species in other families of Algæ. In order to mark the plants so sent to me I have put after each the letter S, in all cases where I had not previously found the plant in Canterbury or elsewhere myself. I have also to thank Professor Nordstedt, of Lund, for sending me papers of his upon Desmidieæ and other Algæ, which have been of great service; also Mr. Joshua, F.L.S., of Cirencester, England, who kindly sent me, a few months ago, a number of tubes containing gatherings of Algæ from various parts of England. In these tubes, although I have not yet thoroughly examined them, I have found, so far, more than fifty species of Desmidieæ, many of which are uncommon, and all have been of great use to me for comparison with the New Zealand forms. My works of reference have been increased since 1880 by the addition of Rabenhorst's “Flora Europæa Algarum,” Pritchard's “Infusoria,” the “Annals and Magazine of Natural History,” and others. Examination of these has not compelled me to abandon any of the species which I set down in my former paper as new, with the exception, perhaps, of Staurastrum (Didymocladon) stella and Docidium dilatatum. The former may possibly be S. furcigerum or S. sexangulare: the latter is said by Mr. Archer to be probably D. ovatum, Nordstedt. I have been fortunate enough in the last two years to find some species of Desmidieæ in conjugation, with attached zygospores, notably Cosmarium

tetraophthalmum, Closterium acerosum, Clost. lineatum, Penium margaritaceum, and a few more. Still, conjugation seems to be very rare here, and Dr. Spencer tells me that it is equally so in Hawke's Bay. By the way, it is curious how capricious the Algæ often seem to be in their appearance and disappearance. For example, two years ago, Micrasterias rotata and M. ampullacea swarmed in some pools. This year both are exceedingly scarce about Christchurch. Volvox globator was to be found, in 1878 and 1879, in myriads: since then I have seen very few, and during the last twelve months not a single specimen. It will be observed that, with the help of the Hawke's Bay gatherings, I have been able to add three genera to the New Zealand Flora, viz., Desmidium, Xanthidium, and Arthrodesmus; but I have not found any of these in Canterbury. The measurements adopted in this paper are expressed in the modern nomenclature which, as I understand, microscopists in Europe are endeavouring to bring into general use. Instead of the old “inch,” and fractions of it, which were only intelligible to Englishmen, micro-measurements are now expressed by the symbol μ, representing a micro-millimetre. One μ = 1/1000 millimetre = 1/25000 inch almost: so that, for example, instead of saying that Micrasterias rotata has a length of 1/90 inch, one would say nowadays 278 μ. This mode is intelligible to observers of all countries, and is undoubtedly preferable to the old one. I regret to say that a little ditch near the Fendalton Road, which has supplied me with some of the most curious of the New Zealand Desmids, including Triploceras tridentatum, Staurastrum aculeatum, and others, will soon be no longer available. At the best it was only a little “grip” in a field, almost dry in summer; and it was always a puzzle to me how so many uncommon forms got there, especially as it could not have existed many years. But now the march of progress is rapidly effacing it, and the streets of the flourishing village of Bryndwr will probably in a few weeks destroy it altogether. The worst of it is that I know no other habitat in Canterbury for some of these forms. Part I. Additions to Catalogue of New Zealand Desmidieæ. 1. Desmidium, Agardh. D. swartzii, Agardh. S. (R. IV.) Not uncommon, apparently, in Hawke's Bay. It has not been found in Canterbury. D. aptogonium, Brébisson. S. (R. XXXII.) I have not seen this plant, which Dr. Spencer informs me occurs very rarely in Hawke's Bay.

2. Sphærozosma, Corda. S. pulchrum, Bailey. S. (R. XXXV.) Occurs in Hawke's Bay, rarely. I have not seen it. Mr. Archer (in Pritch. Inf., p. 724) includes this plant in the genus Spondylosium, as it has no processes uniting the joints. Rabenhorst considers Spondylosium only a sub-genus of Sphœrozosma. 3. Euastrum, Ehrenberg. E. ansatum, Ehrenberg. S. (R. XIV.) Not uncommon. From Hawke's Bay. 4. Cosmarium, Corda. C. ralfsii, var. β, var. nov. Fig. 1. Differs from the normal form only in its size, which is very small. Length in front view, 37.5 μ; breadth, 25 μ. But these dimensions are quite constant, and the larger form has not been present with it in any gathering which I have observed. Were it not for the slightly triangular segments it might be C. cucumis; it cannot be C. pyramidatum, as the frond is smooth. C. thwaitesii, Ralfs. (R. XVII.) Fig. 2. Rare. I am doubtful about this plant, as I find no trace whatever of any gelatinous covering, whether for single fronds or colonies. Ralfs says of it, “puncta very indistinct:” the plant here is smooth. Length, 44 μ. C. pusillum, Brébisson. Fig. 3. This is the smallest plant of the genus known to me. I copy Mr. Archer's description (in Pritch. Inf., p. 731): “Frond very minute, slightly broader than long, constriction acute, segments angulato-trapezoid, slightly narrowing upwards, smooth, angles rounded, ends slightly concave.” I think, however, that the plant here is punctate. The plant is scarcely visible below a power of 200 diameters. Length of frond, 12 μ; breadth, 15 μ. Hitherto described only from France (Brébisson) and Saxony (Raben-horst). Not common. I have specimens dividing, but no zygospores. C. punctulatum, Brébisson. Very similar to a young state of C. margaritiferum: indeed Mr. Archer (in Pritch. Inf., p. 733) unites the two. Rabenhorst is doubtful on the point. Common, both in Canterbury and Hawke's Bay.

C. gemmiferum, Brébisson. S. Fig. 4. A large, handsome species, of the general appearance of C. margaritiferum, covered with conspicuous pearly granules, but differing by having on each segment, at the middle, on both surfaces, a rounded protuberance bordered with granules, which is best seen in end view. (Pritch. Inf., p. 733.) The typical plant has slightly truncate ends; in our species the truncation is sometimes not apparent. Seemingly not uncommon in Hawke's Bay. The European species has only been found, I think, in France. C. obsoletum, Hantzsch, var. punctatum, var. nov. S. Fig. 6. Frond in front view almost circular, the breadth perhaps a little more than the length. Edge smooth. Constriction deep, narrow, linear. Segments broader than long, with a minute, bluntly-triangular process on each at the entrance of the constriction on each side; processes convergent, pointing slightly outwards. End view elliptic, showing the processes. Surface of frond distinctly punctate. Diameter in front view, 60–65 μ. Zygospore unknown. Not uncommon in gatherings from Hawke's Bay. Professor O. Nordstedt, in a paper which he has kindly sent me on some Algæ in the museum of Lund, figures a species from Java—C. obsoletum, Hantzsch, closely resembling the above. The same plant is found in Rabenhorst (Flor. Alg., sect. iii, p. 227) as Artthrodesmus obsoletus, a variety of A. convergens. Neither author, however, gives more than the very briefest description. But Prof. Nordstedt's figure clearly shows his plant quite smooth, without puncta. In other respects I see no difference, and I think the puncta are not sufficient to raise our plant above the position of a variety. C. speciosum, Nordstedt, var. inflatum, var. nov. Fig. 6. Frond in front view elliptical, the ends not at all or very slightly compressed; segments longer than broad, sides convex; constriction deep, narrow, linear. Segments when empty showing rows of minute semi-orbicular granules, the rows apparently radiating from the centre of each segment, but not reaching quite to it, so that the median space would be smooth if it were not for a number of longitudinal rows of smaller granules, which rows, being slightly curved and not all in focus at once, testify to the presence of a central inflation. The result of the two sets of granules is to

New Zealand DesmidieÆ.

give a laterally-grooved appearance to the segment and a minutely undulate appearance to the edge, while the central portion seems longitudinally costate. In side view each segment is angular-elliptic, the end somewhat truncate; and a broadly rounded inflation is distinctly visible at each side. End view elliptic. Length of frond 72 μ; breadth in front view 50 μ; breadth at inflation in side view 37 μ; breadth at constriction 25 μ. Not common: as yet only from the ditch at Bryndwr, near Fendalton, where Triploceras tridentatum occurs, and very rarely in gatherings from Hawke's Bay. I had long been puzzled by this plant, and had come to the notion that it might be a new species. But my English gatherings from Mr. Joshua have been useful here. One of them is labelled, “C. speciosum var. biforme, Nordstedt,” and seems to contain scarcely any other Desmidieæ; and the European plant appears to correspond closely with ours. The differences are, that in the New Zealand plant the central inflation is quite distinct, especially in side view, and the ends are either round or only compressed very slightly, in front view. I rather think also that the granules are smaller than in the English form. I have met with no description of the European C. speciosum. Neither Ralfs, Rabenhorst, nor Pritchard mentions it; and the only reference which I have found in Professor Nordstedt's papers is a statement that it occurs very sparingly in the Sandwich Islands. The term “biforme” attached to my English specimens refers, I presume, to the fact that some of them approach in outline rather to C. botrytis. C. cyclicum Lundell, var. ampliatum, var. nov. Fig. 7. Frond in front view orbicular, each segment being about twice as broad as long. Constriction linear, not deep, gaping. Segments when empty showing a number of minute semi-orbicular granules, arranged in rows radiating from the centre, so as to give a grooved appearance to the frond and an undulate appearance to the edge. The ends are not at all compressed. End view elliptic: the edge undulate. Diameter of frond in front view, either way, about 50 μ: breadth at constriction 25 μ. Rare: as yet only from a ditch on the Sumner Road, near Lyttelton, in company with Penium margaritaceum.

I have not seen Lundell's description of his plant, which appears to be very rare in England. But, in the “Midland Naturalist,” vol. iv., 1881, I find C. cyclicum figured by Mr. A. W. Wills, without description. Assuming, as is most probable, that this figure is accurate, the English plant differs from ours in having a deep narrow constriction, so that the segments approximate quite closely and indeed touch each other. In the New Zealand variety the wide shallow constriction is quite conspicuous, and the segments diverge from each other at once. C. botrytis, Bory. (R. XVI.) In my former paper I expressed doubts as to this species; but many specimens have since come under my observation and there is no doubt that the plant occurs here plentifully. It is common near Christchurch and in the Cust Valley. C. tetraophthalmum, Kützing. (R. XVII, XXXIII.) Var. α, the large form. S. I have no specimens from Canterbury which I can with certainty refer to this plant, but several occur in gatherings from Hawke's Bay. I see no difference between it and the English plant. Var. β, the small form. Fig. 8. The frond is small, more orbicular than in var. α, the segments being broader than long and the pearly granules are much smaller, indeed inconspicuous. I should not have considered the two as the same species, were it not that in one of Mr. Joshua's English gatherings I find a plant (apparently identical with this) which is labelled “Cos. tetraophthalmum, small form, zygospores, not botrytis, fide Nordstedt.” In that gathering are some specimens in conjugation, and I have been fortunate enough to find one here also in the same condition, as shown in my figure. I may observe that Ralfs, in his description of the large form, says,—“the sporangia are large and their spines finally branched;” but in his pl. xxxiii. he figures the spines as subulate. Those of my English specimens are also subulate, but probably in both instances the zygospores are not mature. Length in front view, 44 μ; breadth, 40 μ; diameter of zygospore, including spines, 65 μ. Rare: from Lyttelton. C. undulatum, Corda, var. β, var. nov. (?) Fig. 9. The distinctive character of this plant is its small size, the length being only 33 μ, the breadth about the same. In Ralfs' plate xv. two sizes are shown, but both are larger than our plant, and the measurement given in the same work is, length 1/416 of an inch, or about 63 μ.

C. tenue, sp. nov. Fig. 10. Frond sub-orbicular, the segments slightly broader than long. Ends rounded. Edge smooth; constriction deep, narrow, linear. Frond neither punctate nor granulate. A single starch vesicle is visible in the centre of each segment. End view elliptic. Length of frond 15.5 μ; breadth at constriction 3 μ. Not common: my specimens were all found amongst Chara, in running water, near Christchurch. This is a very minute plant, scarcely larger than C. pusillum. It nearly resembles C. bioculatum, Brebisson, but differs in the absence of the distinct isthmus which, according to Ralfs, connects the segments of that species, and in having a deep and narrow, instead of a wide and gaping, constriction. C. exiguum, Archer (Micr. Journ., 1864, pl. vi.), has oblong segments. I find none of the minute Cosmaria described exactly corresponding to this form. It has not the colour of C. tinctum, Ralfs. 5. Xanthidium, Ehrenberg. X. cristatum, Brébisson. S. (R. XIX.) I have not found this plant in Canterbury. It seems to be not uncommon in Hawke's Bay. X. aculeatum, Ehrenberg. S. (R. XIX.) Same remark as for the last species. 6. Arthrodesmus, Ehrenberg. A. incus, Brébisson. S. (R. XX.) Only from Hawke's Bay. A. convergens, Ehrenberg. S. (R. XX.) Only a single specimen observed, in a gathering from Hawke's Bay. The spines on the ends of the segments in this specimen were sigmoid, bending slightly outwards. 7. Staurastrum, Meyen. S. dilatatum, Ehrenberg. (R. XXI.) Not uncommon. S. alternans, Brébisson. (R. XXI.) Rare. S. tricorne, Brébisson. S. (R. XXII.) I cannot identify any of my Canterbury specimens with this form, which appears to be common in Hawke's Bay. Rabenhorst considers the two last as only varieties of S. dilatatum. The distinction between S. alternans and S. tricorne is very slight, depending upon a minute prolongation of the angles of the latter into short processes.

S. punctulatum, Brébisson. (R. XXII.) Common. Distinguishable from S. dilatatum chiefly by the more turgid segments and generally rougher frond. S. aculeatum, Ehrenberg. (R. XXIII.) Not common: as yet only from the Bryndwr ditch. It is curious that this ditch, perhaps twenty yards long, a couple of feet wide, and a few inches in depth, should have contained so many species of Desmidieæ, most of them too of great interest and beauty. S. spinosum, Brébisson. (R. XXII.) Very rare: indeed I am not sure that this plant occurs here. Rabenhorst makes it only a variety of S. (Xanthidium) furcatum, Ehr., a plant which Ralfs mentions only doubtfully. Some specimens in gatherings from Hawke's Bay were referred by Dr. Spencer to this species, but on close examination appear to me to be rather the next. S. eustephanum, Ehrenberg, var. emarginatum, var. nov. Fig. 11. Frond in side view deeply constricted at the middle: the constriction wide, gaping. Segments sub-elliptic, the lateral margins convex or turgid, the outer margins nearly straight, sometimes concave. At each angle appear three spines, not in the same plane: the terminal spine long, subulate, tipped with a sharp awn, the two others shorter, cylindrical, forked at the tip. These processes are quite smooth, but I think there is sometimes a minute punctation on the frond. In an empty frond the terminal processes of the third angle can be seen foreshortened on the segments. There are no processes on the edges, except at the angles. Frond in end view triangular, the sides of the triangle emarginate, or widely crenate, being a little inflated at the middle. Each angle terminates in a somewhat elongated cylindrical or subulate process tipped with a sharp awn. On the sides, close to the angles, are seen six other processes, shorter than the terminal ones, cylindrical, and forked at the tip, and the bases of these are conjoined; they are not on the plane of the triangle, so that they present somewhat the appearance of a star with six short rays. At the base of the fork, on each process, there is an exceedingly minute spine. The processes are smooth and project a little beyond the sides of the triangle, not perpendicularly to the sides but pointing somewhat towards the angles. The whole plant is very minute; average length of segments in side view (exclusive of processes) 23μ: length of side of triangle in end view (exclusive of awns) 25μ; length of awns 4μ.

At first sight this plant might be taken, in side view, for S. spinosum, or in end view for S. monticulosum, Brébisson. But it differs from the former in having its outer edges less turgid than the inner and in its processes not being on the same plane; from the latter in the more cylindrical lateral processes and their forked tips. The nearest resemblance to it is, I think, S. (Desmidium) eustephanum, Ehrenberg, an American plant, referred to by Ralfs, p. 215, without figure, and described and figured in Pritchard's Infus., p. 743 and pl. ii., fig. 3. The differences are that in the New Zealand plant the sides, in end view, are emarginate and not rectilinear as in the American variety, and the lateral processes project beyond the sides, whereas in Pritchard's figure they are very small and do not reach the sides. In S. senarium, Ehrenberg (also American), similar processes project, but there is àlso a second series of six others, shorter and in almost corresponding directions, behind the first. In the “Midland Naturalist,” vol. iv., pl. v., Mr. A. W. Wills figures S. pseudofurcigerum, Reinsch, not unlike our plant in end view, but it is covered with minute spines on the processes as well as on the frond, and the side view is also different. On the whole, I take this plant to be intermediate between S. eustephanum and S. senarium. S. clepsydra, Spencer (in lit. cum specim.), sp. nov. S. Fig. 12. Frond somewhat large, smooth. Segments in side view broader than long, widening rapidly from the constriction which is not deep. The external edges are either straight or oftener slightly concave: lateral edges convex. Ultimate angles ending in a fine awn or mucro. In consequence of the shallow constriction the segments are closely united at the base, the junction is broad, and there is no isthmus or band whatever. The apex of the third angle with its awn is usually visible beyond the external edge of each segment. Frond in end view triangular; the sides equal, slightly concave: somewhat mammillate at the angles which are terminated by the awns. The concavity of the sides is not always conspicuous. Frond quite free from puncta. I have seen no zygospores attached to fronds, but in every gathering there are a number of bodies which may not improbably belong to this plant. They resemble generally those of S. dejectum, but have fewer spines. I have been able to compare them not only with Ralfs' figures of S. dejectum, but also with zygospores of that species in my English gatherings. Length of frond in side view 31–40 μ; breadth at external edge of segments (exclusive of awns) 30–35 μ; breadth at constriction 15–17 μ; side of triangle in end view 30–35 μ; length of awn 5 μ.

It appears to be abundant in Hawke's Bay, at least in one locality. I have not found it in Canterbury. This plant at first sight bears great resemblance to S. dejectum, Bréb., and indeed, when seen in end view, is not to be distinguished from that plant. But, as Dr. Spencer remarks in his letter to me, the broad junction of the segments in side view renders it distinct. Ralfs observes of S. dejectum that “its segments are connected either without a band or with a very short one:” the expression of Rabenhorst is—“sinu amplo, acutangulo vel obtusangulo;” but no conclusion could be drawn from either phrase that the segments of the European plant are so closely and broadly joined as those of S. clepsydra. Indeed, Ralfs gives the breadth at constriction of S. dejectum as 1/2732 inch, which is much smaller than that of the New Zealand plant. If S. cuspidatum, which differs from S. dejectum chiefly in the length of its connecting band, is considered a good species, the same rule might well be observed for S. clepsydra. S. cuspidatum, Brébisson. (R. XXI.) Not common. Two specimens from Canterbury, and a few from Hawke's Bay. S. (Didymocladon) furcigerum, Brébisson. S. (R. XXXIII.) Fig. 13. The specimens which I have seen have all either five or six radiating processes in end view. Rabenhorst unites Didymocladon with Staurastrum, and says that the plant may have 8–4–6–7–8–9 rays: he omits 5. In all my specimens the rays in focus at the extreme end have the other series behind them in exact, or almost exact, correspondence with them, as shown in my figure. For comparison with my D. stella (Trans., vol. xiii., p. 308) see below, under that species, in the second part of this paper. Only from Hawke's Bay, where it seems to be not uncommon. 8. Penium, Brébisson. P. margaritaceum, Ehrenberg. (R. XXV. and XXXIII.) I have specimens which, I think, can be referred to all the three varieties, α, β and γ of Ralfs. Rabenhorst unites the two first, and indeed here they all occur mingled together. As for the third, the main difference between it and the others, in England, appears to be the smaller size of its granules. None of my specimens show such large granules as are figured by Ralfs, but some are slightly constricted at the middle, while others show no constriction. I was fortunate enough to find, on one occasion, a large quantity of this plant in full conjugation, with attached zygospores: there seems to be nothing to distinguish it from the English species.

From the Sumner Road, Lyttelton, and very rarely from the Cust Valley. P. jenneri, Ralfs. (R. XXXIII.) or P. brebissonii, Meneghini. (R. XXV.) I have great doubts which of these two occur here, or indeed whether either has come under my observation. Possibly I have mistaken Cosmarium thwaitesii for it. If P. brebissonii always occurs in colonies in mucous strata, then I have not seen it. Very rare, in any case. 9. Triploceras, Bailey. I observe that Rabenhorst and other algologists place this genus, with some of the Docidia, under Naegeli's genus Pleurotanium, so that probably Bailey's name must be given up. T. tridentatum, mihi, var. cylindricum, var. nov. In vol. xiii. of the Trans., p. 311, I described a plant of this species with a rectangular section. The present variety is circular in section, and of a generally thicker form. Otherwise there seems to be no difference, and the two are found together. From the Bryndwr ditch, and also, rarely, from Hawke's Bay. 10. Closterium, Nitzsch. C. griffithii, Berkeley. Fig. 14. Fairly common. Length, from 110–160 μ. C. venus, Kützing. I see that Rabenhorst considers this as a separate species, though Ralfs unites it to C. dianœ. As far as I can make out, the main difference between the two is that C. venus is the smaller. However, the dimensions appear to be constant. C. ehrenbergii, Meneghini. (R. XXVIII.) Not uncommon. Distinguishable, especially from C. selenœum, mihi, by its thick rounded ends and by a conspicuous median inflation of the inner margin. As to this, see below, under C. selenœum, in Part II. of this Paper. 11. Spirotænia, Brébisson. Sp. obscura, Ralfs. Very rare. This plant is subject to the same disadvantage as Sp. condensata. Its distinguishing character is the spiral endochrome and this is quite destroyed by all the preserving fluids which I have tried. 12. Scenedesmus, Meyen. Rabenhorst relegates this genus to the Palmellaceæ but as other authors include it among Desmidieæ I leave it.

S. acutus, Meyen, var. dimorphus, Kützing. (R. XXXI.) The cells are pointed, closely arranged in a single even row and the two outer ones are lunate. Not common. S. obtusus, Meyen. (R. XXXI.) The cells are ovate or oblong and not in an even straight row. Common. Part II. Notes on some of the Desmidieœ described in my former paper. Trans. N.Z. Inst., vol. xiii., 1880, p. 297. I have had the advantage lately of perusing, in vol. x. of “Grevillea,” No. 53, Sept. 1881, an article by Mr. Archer reviewing my paper on New Zealand Desmidieæ. It has been a great satisfaction to me that so acknowledged an authority does not find grave fault with the descriptions which I gave of my new species, nor, in general, with the paper itself; and Mr. Archer's remarks have gone far to clear up some points upon which I have been in doubt. I take this opportunity of referring again, in a more or less explanatory way, to some of the plants therein mentioned, as well as to some others that Mr. Archer makes no comment upon. Previously, however, I must touch upon a point referring to the whole family. Mr. Archer agrees with me in thinking that there is great reason to believe many of the Desmidieæ to be cosmopolitan, but he goes on to remark that my “identifications of certain species may not be thoroughly correct.” The same thought was certainly in my own mind when writing my paper; and in my introductory remarks I observed that “in many of the species which I have set down here as European, more especially perhaps in the genus Cosmarium, I have noticed peculiarities which do not seem to have been mentioned by authors. The discussion of these would lead me beyond the scope of this paper and perhaps the characters to which I refer would not even suffice to raise the plants even to ‘varieties.’” In point of fact, three reasons prevented me from attempting to differentiate these plants from European species. First, the dearth of works of reference, for it was impossible to tell whether the minute characters noticeable were referred to or not by any author elsewhere. Secondly, a doubt whether these characters might after all only have been overlooked, or erroneously referred to, by previous observers; and an instance of this is afforded me in Mr. Archer's paper in “Grevillea,” where Staurastrum avicula is stated to be really, in England, “not a smooth species, but rough,” and this was a plant regarding which I expressed doubts in my paper and which

is now stated to have been wrongly figured in Ralfs. And, thirdly, I was unwilling, unless fortified by more evidence, to multiply species and varieties or to introduce confusion, if I could help it. Mr. Archer's doubts as to some of my identifications are therefore, I confess, not unwarranted, and it is quite possible that future observers, noting the peculiarities of our New Zealand Desmids, minute as these peculiarities often are, may go beyond me and endeavour to raise the plants to distinct rank. Still, even now, when I have had the advantage of longer examination and extended means of reference, I hesitate to do so. In the cases of some plants, specially mentioned in Mr. Archer's paper, notes and explanations will be found in the following pages: as regards many of the others, want of time has prevented me from devoting to them so close an observation as would be necessary to elucidate such minute features. As will be seen below, I am almost tempted to boldly make a new species of the plant which, in my former paper, I referred to Micrasterias rotata; but even in that case I refrain from doing so. Sphœrozosma excavatum, Ralfs. I find that this plant is somewhat less rare than I thought it to be; but still I can by no means consider it common: and in consequence of its great fragility connected filaments are found much more seldom than separate joints. Micrasterias rotata, Greville; and Micrasterias denticulata, Brébisson. Fig. 16. With regard to the distinction between these two, I find from Mr. Archer's paper that that there is no doubt about it, owing to the difference between the zygospores. These I have never yet seen, and my only means of distinguishing were the teeth of the lateral lobes; and as both sharp and truncate teeth are found here indiscriminately, sometimes all round the frond, sometimes sharp on one segment and truncate on the other, sometimes both sharp and truncate on the same segment, I am still greatly in doubt whether M. denticulata occurs here at all. And now as to our M. rotata. Is it identical with the English plant, or so nearly so as to be considered the same, or shall it be erected into a new species? Here my doubts arise from the second of the sources mentioned just now; that is, an uncertainty whether some of the features noticeable here may not occur in European plants but have been either overlooked by authors or mentioned somewhere unknown to me. The first difference is size. According to Ralfs the dimensions of M. rotata are,—length, 1/91 inch; breadth, 1/104 inch: and Rabenhorst's measurements apparently agree with this. Reduced to modern nomen-

clature this would be: length 274 μ; breadth, 240 μ. All my New Zealand specimens which I can consider as full grown have a length not less than 320 μ, and many range as high as 400 μ. The average difference is shown in the diagram, fig. 16d. Secondly, I think the teeth of the lateral lobes are more numerous, and sharper, than those of the European plant, supposing that is that Ralfs' figure may be taken as the general form. My figure 16a shows the number and character of the teeth in a full-grown plant. Thirdly, and this is probably an important character, the extremity of the end lobe shows divisions which I am not sure that I find in previous descriptions. As shown in fig. 16a, and more highly magnified in 16c, the extremity of the end lobe has the two teeth at the angles, but it is also deeply divided by a median elliptical cleft, and at the opening of this cleft, on each side, are two short spines or teeth, each pair converging so as almost to close the cleft; and the pairs are not on the same plane, the lower ones appearing as if from a mammillate inflation on the subdivision of the lobe. Are these specific distinctions? I am not prepared to say. With regard to the last, Rabenhorst's phrase is—“lobo polari angusto cuneato prominulo, in apice plus minus profunde sinuato- vel undulato-exciso, angulis oblique truncatis vel bidentatis.” Mr. Archer (in Pritchard, Inf. p. 727,) says, “End lobe very slightly exserted, its angles very slightly produced, bidentate, ends emarginate.” Possibly neither phrase can be construed to include such a cleft as that shown in our plant. As for the spines, they might at first sight be taken for those of M. fimbriata, but they are less hairlike than in that plant, and besides there is never any sign whatever here of the spines seen on the teeth of M. fimbriata, in the lateral lobes. In my figure 16b I represent a specimen which only once came under my notice, amongst perhaps a dozen of the ordinary form, and which I take to be a young state of the plant. It is smaller in size, but the cleft of the end lobe is there. The angles of that lobe are scarcely bidentate, and the spines at the cleft are inconspicuous. And the teeth of the lateral lobe are of irregular form, some truncate, some sharp. It appeared to me that the specimen was certainly immature. On the whole, I hesitate yet as to the identification of this plant, and being unable to make up my mind on the point, leave it as M. rotata. In the character of the endochrome, in the arrangement of the amylaceous vesicles, and in the mode of self-division (as noted in my former paper) it resembles the European species. When a zygospore is found, the doubt may be cleared up, but we may have to wait some time for that.

I have already mentioned that this plant, which was common here two years ago, has been very scarce of late: and no sign of conjugation has as yet come under my observation. Holocystis incisa. Mr. Archer unites this to Micrasterias (other authors, I find, include it under. Tetrachastrum); and he states that instead of being identical, as I had thought, with Dr. Wallich's Indian plant, it is probably the same as a plant from Sweden, reported by Cleve and called M. decemdentata β upsaliensis. Euastrum binale, Turpin. The plant mentioned by me (vol. xiii., p. 306) as either this or E. elegans is certainly E. binale, as I have satisfied myself by comparison with Ralfs' figures, and with specimens in my English gatherings. E. elegans shows the sides of the terminal notch extending considerably beyond the lateral spines. I regret to say that the figure 26 in vol. xiii., pl. xii., is about as unlike the plant which it is supposed to represent as it is possible to be; and unluckily Mr. Archer has been misled by it to take my Euastrum for a new thing. My original drawing was meant to be, and I think was, almost exactly resembling Ralfs' figure 8 d (or 8 f) in his pl. xiv. Cosmarium margaritiferum. I believe that several of the forms supposed by me to belong to this species were really C. tetraophthalmum, C. broomeii, etc., or at least closely allied to them. C. biretum I have never seen here: C. botrytis is certainly common. The conjugation of C. margaritiferum I saw once, and could detect no difference from the European plant. In this case also the printed figures in pl. xii., vol. xiii., figs. 27, 28, and 29, are unsatisfactory. Fig. 28 was intended to show a slight truncation, but it does not show any. Cosmarium crenatum, Ralfs. Fig. 15. If Ralfs' figure 7, pl. xv., be correct, our New Zealand form differs from the English one by having its ends (as my figure shows) straight, without crenations. I think also that the segments are somewhat wider at the base. Length of frond 30.5 μ; breadth 27 μ. Cosmarium botrytis, Bory. In examining this plant I have been able to detect a very decided voluntary motion, which on one occasion I observed for nearly three hours. As far as I can gather from works available to me, it has never been satisfactorily shown that the Desmidieæ travel voluntarily, that is, in the manner in which Diatoms travel. It has long been known that Desmids “move;” that is, they will come to the surface if buried in mud, or to the side of a vessel nearest to the light. But such movements as these, as Ralfs remarks (p. 22), may be due rather to the stimulus of light than to “voluntary

effort.” Many observers have recorded notes on this subject. Ralfs quotes the following:—“It was impossible to determine whether the vague motions of Closterium were voluntary or not” (Dalrymple):—“I have seen Euastrum margaritiferum move quite distinctly” (Bailey):—“Elles n'ont pas un mouvement sensible sur le porte-objet du microscope” (Brébisson)— contradictory assertions evidently. Mr. Archer (in Pritch. Inf., p. 5) says that “the Desmidieæ are seen to move. * * * * This phenomenon is most notable in Closterium; in others it is scarcely, in many not at all, cognizable.” The Rev. Mr. Osborne, in the Journ. of the Micros. Soc., ii., 235, attributes the movements of Closteria to cilia, but no other observer seems to agree with his views. A friend of mine tells me that he has frequently seen Cl. lunula “rolling over and over.” But none of these statements appear to me to satisfactorily settle the question whether the Desmids do voluntarily travel, in any willed direction, as the Diatoms do, or whether the movements observed may not have been due to some currents in the water or disturbing influences beyond the field of the microscope at the moment. I venture, therefore, to give a few notes of the motions observed by me in Cosmarium botrytis, motions which I believe to have been perfectly “voluntary,” and not due to any external influences. I had been observing the plant on a morning during the present spring, and comparing it with some specimens in my English gatherings. The specimen under observation was situated in the centre of my “field,” in a small clear space between a dead Pinnularia and a small speck of dirt. It had been stationary for quite an hour, and there was no appearance during that time of any “swarming” within it. The day was fine, and an even full light came through the diaphragm. All at once I detected a commencement of “swarming,” quite faint at first; and when this had continued two or three minutes, I observed a slight oscillation of the frond. By degrees the oscillation increased, and the Desmid began clearly to move from its place. Soon the motion increased, and the plant steadily worked its way out between the Pinnularia and the dirt, not gliding straight-forward but jering along, with a motion exactly like that of a man elbowing his way through a crowd, pushing forward first one side and then the other. It was clear that the Pinnularia could not produce any effect on it, as it was dead; and I carefully looked to see whether anything in its neighbourhood could have set a current in motion, but found nothing. In about ten minutes the Cosmarium had jerked or elbowed itself out into the open water, and still continued its journey towards the apparent lower edge of the slide. Five minutes after, the “swarming” somewhat increased, as did also the oscillation; and the plant then stopped and began (also in jerks)

to raise itself on end, an operation which it took four minutes to complete. Having attained an upright position it remained there two minutes, waving gently to and fro, and then, all of a sudden, fell over on the other side. The “swarming” had now become quite violent, and the plant recommenced its travels, but this time in the contrary direction, returning towards the Pinnularia; after continuing thus for a minute or two it stopped, and then once more travelled away again. For half an hour it continued these manœuvres, sometimes going one way, sometimes another, always “elbowing” its way along, and in the main getting farther away from its original spot. Sometimes, when it stopped, it would roll about from side to side rather violently (but never from end to end). I thought I observed that as the “swarming” increased, so also did the “jerks,” and it appeared to me also that the endochrome was changing. It showed a tendency to form in each segment two masses of closer consistency than the rest; each of these masses, retaining its bright green colour, became surrounded with a brownish band, and it was in this band (never in the green particles) that the swarming was conspicuous. Once an exceedingly minute Infusorium, scarcely visible under the ⅓ objective, came sailing towards the plant, somewhat leisurely; but, when almost on the point of touching it, darted suddenly back to some distance. Was it repelled? I could not say: it did not return. The oscillations and rollings of the Cosmarium continued for two or three hours, and I observed that whenever it chanced to come to any little mass of weed or dirt obstructing its course it avoided it, sometimes indeed retracing its steps a little to get round a headland. Whenever it raised itself on end I took especial pains to see whether anything could be observed of the nature of cilia, or whether any appearance could be detected in the water leading to the supposition that retractile processes existed, but without success. I have no doubt that the movements described were quite as “voluntary,” as those of any Diatom. In another part of the same slide a Stauroneis was travelling very actively and the difference between the two plants was that the Diatom glided backwards and forwards without more than very slight oscillation, whereas the Cosmarium made its way simply by lateral jerkings. Staurastrum gracile, Ralfs. Fig. 17. This is another of the plants in which the differences from the European form do not seem to me to be sufficient to render it distinct. As my figure shows, it is less slender and the processes are shorter than in Ralfs' species. Length in end view from the middle of one side to the end of the opposite process (exclusive of the four spines) 50 μ: length of process 15 μ.

Staurastrum avicula, Brébisson. Mr. Archer thinks that our plant may be a distinct form and says that Ralfs' figure of the English species is incorrect. I am willing to accept this, but as I have not seen any specimens since writing my former paper I am not prepared to suggest any new name. All these minute forms of Staurastrum are difficult of identification and it would be easy to multiply species upon the slight differences occurring so frequently Didymocladon stella, mihi. This plant must, I suppose, be relegated to the genus Staurastrum, as Pritchard, Rabenhorst and succeeding writers do not admit Ralfs' genus. As to its specific status, I am in some doubt. After carefully comparing it with specimens of S. furcigerum, both from Hawke's Bay and from England, and allowing for Rabenhorst's statement that S. furcigerum may have from three to nine rays in end view, I cannot regard my S. (Didymocladon) stella as identical with that plant. In all my specimens of S. furcigerum, as remarked in the first part of this paper, whether there are five or six rays, those rays which are behind the terminal ones, and which are at first sight out of focus, are always in almost, if not quite, direct correspondence of direction with the terminal rays. I cannot see how in any case the peculiar multi-radiate appearance of S. stella can be produced by the English plant. I find, however, in the “Midland Naturalist,” a figure (vol. iv., pl. v.) of Staurastrum arctiscon, Ehrenberg, a plant mentioned by Rabenhorst as American, under the name Xanthidium arctiscon, and seemingly found lately in Wales. This plant, in end view, has six terminal rays, and eight others behind them, almost in corresponding directions. Whether, in some cases, it may show the twenty-eight divaricating rays of my S. stella I cannot say: if so, my plant will have to be abandoned as a distinct species. S. pseudo-furcigerum, Reinsch, though its side view approaches best to that of S. stella, differs altogether in end view, being then more like S. austephanum in general outline. I find that Mr. Archer would refer our plant rather to Staurasirum sexangulare, Bulnheim, which I do not know. Docidium baculum, Ehrenberg. I expressed in my former paper doubts as to the existence of this plant here, and after comparison with English specimens I have come to the conclusion that it is not found here, or at least that it has not come under my notice. Its distinctive character is the possession of a solitary, prominent inflation at the base of each segment. All my New Zealand specimens show at least more than one inflation.

Fig. 19. Two of the distinguishing marks separating this plant from C. ehrenbergii are—the acuteness of the ends and the absence of a median inflation of the inner margin. The first character is constant and conspicuous. With regard to the second, I find that although, in its natural state, the inner margin forms a clear concave curve, yet in all the preserving fluids which I have tried an inflation becomes noticeable; not indeed such an inflation as that of C. ehrenbergii, but of the nature of that shown in my figure, where the inner margin becomes nearly straight. Indeed, in glycerine, it is sometimes quite straight. I find also that when fronds are about to conjugate, an inflation is noticeable on both the outer and the inner margin, but only in the immediate region where the suture should be; that is, the cell-wall at that particular spot is bulged out all round. This, which is part of the process of conjugation, as I am about to describe, is quite different from the wide inflation visible in C. ehrenbergii. The process of conjugation, however, as I have lately been fortunate enough to see up to a certain point, is the same as in C. ehrenbergii, as described by the Rev. W. Smith, in the Annals and Mag. of Nat. Hist., 1850, p. 1, and pl. i. Two fronds, each of which presents the slight bulging at the middle just mentioned, approach each other, and then become surrounded by a mucous envelope, within which they lie, longitudinally approximate, their ends almost touching, and their concave sides turned towards each other. Next, they proceed to undergo self-division: each frond separates at the middle, drawing itself out until, after the separation, there appear four fronds, each with one long arm and one very short arm, the latter terminating in a rounded short beak. Then the conjugation takes place by the junction of each corresponding pair, the junction being operated at the point where the bases of the long and short arms occur: and the endochrome, pouring out from each frond and joining in the middle, forms the zygospore, or, rather, the two zygospores, as there is one to each pair. Unfortunately, I cannot say precisely the nature of these zygospores. The specimens which I observed had been placed in a growingcell, where the process just described had been going on quite smoothly for more than twenty-four hours, from the first approach of the fronds down to the junction of the endochrome. At this point a sudden jar displaced the thin cover-glass of the cell: the conjugating fronds were crushed, and the process was at once brought to an untimely end. However, from what I saw, and from the presence in the gathering of bodies not otherwise identifiable, I have no doubt that the zygospores of C. selenœum are orbicular and smooth.

Mr. Smith (loc. cit.) says that Closterium ehrenbergii stands alone amongst the European Closteria in producing double zygospores. It is, therefore, not uninteresting to have to add to it in this respect a plant from New Zealand. But I have some doubt whether Mr. Smith's statement is altogether correct, in view of a noticeable feature in the conjugation of the next plant on my list, which affords, I think, foundation for a closer study of the phenomenon in connection with other plants of the genus. As a rule the conjugation of Closterium is, in a sense, simple enough: two fronds approach, join, open at a suture, and a zygospore is formed between them. If, as in C. rostratum, the fronds open at the median suture, the segments attached to the zygospore will be equal in length: should there be secondary sutures as in C. intermedium, the fronds may open at these and the segments will be unequal, but the inequality will be easily intelligible. In the case of C. acerosum, Schrank, Fig. 18. the process, to a certain extent, resembles that in C. seleœum. That is to say, the segments attached to the zygospore are unequal, although there are no secondary sutures. The inequality is shown in my figure 18 b, where each frond has one long arm and one very short one. This inequality is also shown in Ralfs' plate xxvii, but no reference is made to it in the text. Mr. Archer, in Pritchard's “Infusoria,” likewise says nothing of it. Von Siebold, in the Journal of the Micros. Society, 1853, seems to refer to something of the kind, though I do not understand his expression: he speaks of “only the two upper and lower halves” coalescing, a phrase which may mean anything. In the spring of last year I gathered on one occasion a small quantity of C. acerosum in conjugation. Although unable to watch the process from its commencement, I examined the gathering with great care. There must have been several hundreds of plants in it, and they were all surrounded with a common mucous envelope, and not segregated in pairs as in C. selenœum. When the mass was first placed on the slide many of the fronds were already in full conjugation, and many others had completed the process. A small proportion (less than one in ten), presented the normal form of the plant, with two equal arms, as in my figure 18 a, the uppermost figure. A few more appeared as the second shown in fig. 18 a, and the rest had still shorter arms, the greater number of all being as in my lowest figure, with one arm almost an equilateral triangle. Conjugation invariably occurred between two fronds of this last form, never in any of the others. If, in the conjugating fronds, I had detected any folds or wrinkles in the cell-wall of the shorter arms, I could have concluded that in the process that arm, for some reason or other, shrank up. But no such folds were

New Zealand Desmidieæ.

visible in any case, beyond, that is, the folds due to the bursting of the cell-wall, which were easily recognizable. Consequently, I could only infer that the fronds had undergone self-division previous to conjugation; and on this supposition those in which the inequality was but slight would have simply missed conjugation and were growing in the ordinary way. This being the case, if I am right, it results that each pair of segments in C. acerosum produces a zygospore, and therefore each whole frond produces two zygospores; but the process differs from that of C. selenœum and C. ehrenbergii in this, that the fronds do not shut themselves up in pairs in mucus, but are all enveloped in the same envelope. Certainly, I cannot say that I saw any fronds dividing, for the process had already begun, and was in full swing when first seen. But I am unable to account in any other way for the curious inequality of the arms. As C. acerosum has only a suture at the middle, and no secondary sutures, the bursting of the cell-wall anywhere but at the middle cannot be explained as in C. intermedium. Penium margaritaceum and other plants also open unequally, but they too have secondary sutures. Closterium lineatum, Ehrenberg. This is another of the plants observed conjugating. There is nothing to distinguish it from the English species. Closterium dianœ, Ehrenberg. Also observed conjugating. I add a figure (20) of Scenedesmus quadricauda, to show the three bristles sometimes observable. Also two figures, 21 and 22, as specimens of the curious monstrosities of growth often seen amongst Desmidieæ, a family generally of such remarkable symmetry of form. Fig. 21 is Tetrachastrum (Holocystis) incisum; fig. 22 is Docidium clavatum. Nominal List of Desmidieæ Reported from New Zealand up to 1882. An asterisk in this list marks the species described by me as new in the foregoing and my previous paper (vol. xiii., 1880, p. 297); a dagger marks those described as new by Dr. Spencer in his paper (vol. xiv., pp. 295, 296); and a double dagger those reported by Dr. Spencer in the same paper, but not new. [Note.—I include also Docidium (Pleurotœnium) ovatum, of which I find the following notice in one of Professor Nordstedt's papers—“Hæc species quoque in Brasiliâ et Novâ Zealandiâ lecta est;” but I do not know the plant.] Hyalotheca dissiliens. dubia.† † Aptogonum undulatum.* Desmidium aptogonium. swartzii. Sphærozosma excavatum. fliforme. pulchrum.† † vertebratum. Micrasterias ampullacea.*

Micrasterias ampullacea, var. β † denticulata? rotata. thomasiana? Tetrachastrum (Holocystis) incisum. Euastrum ansatum. elegans. Cosmarium botrytis. broomeii. crenatum. cucumis.† † cyclicum, var. ampliatcum.* gemmiferum. granatum. margaritiferum. meneghinii moniliferum. obsoletum, var. punctatum.* ornatum? phaseolus. punctulatum. pusillum. pyramidatum. ralfsii. " var. β * speciosum, var. inflatum. * tenue.* tetraophthalmum. † † " var. β. thwaitesii? undulatum. " var. β * sp.† Xanthidium aculeatum. cristatum. Arthrodesmus convergens. incus. Staurastrum aculeatum. alternans. avicula. clepsydra.* cuspidatum. dejectum. dilatatum. eustephanum, var. emarginatum. * furcigerum. Staurastrum gracile. muticum. orbiculare. paradoxum.† † polymorphum. punctulatum. spinosum. (Didymocladon) stella. * tetracerum. tricorne. sp.† Penium brebissonii? closterioides. digitus. jenneri? margaritaceum. Docidium clavatum. dilatatum.∥Docidium dilatatum will have to be eliminated if it is really D. ovatum. ehrenbergii. ovatum (teste Nordstedt). truncatum. Triploceras tridentatum. * " var. cylindricum.* Closterium acerosum. acutum. " var. tenerrimum. † † attenuatum.† † cornu.† † dianæ. didymotocum. ehrenbergii. griffithii. jenneri.† † juncidum. lanceolatum.† † leibleinii. lineatum. lunula. moniliferum.† † rostratum. selenæum. * setaceum. striolatum. venus. Spirotænia condensata. obscura.

Ankistrodesmus acutissimus. falcatus. sp.* sp.* Scenedesmus acutus. "var. dimorphus. obliquus. obtusus. Description of Plates XXIV, and XXV. Fig. 1. Cosmarium ralfsii, var. β. x 350 " 2. Cosmarium thwaitesii x 700. " 3. Cosmarium pusillum, dividing x 1,000. " 4. Cosmarium gemmiferum (a, front view x 350: b, end view x 400) " 5. Cosmarium obsoletum, var. punctatum (a, front view: b, end view x 350. " 6. Cosmarium speciosum, var. inflatum (a, front view: b, side view) x 450. " 7. Cosmarium cyclicum, var. ampliatum (a, front view: b, end view) x 350. " 8. Cosmarium tetraophthalmum, var. β (a, conjugation with zygospore: b, front view: c, end view) x 350. " 9. Cosmarium undulatum, var. β x 700. " 10. Cosmarium tenue (a, front view: b, end view) x 700. " 11. Staurastrum eustephanum, var. emarginatum (a, side view: b, end view) x 700. " 12. Staurastrum clepsydra (a, b, side view: c, d, e, f, end view: g, zygospore?) x 400. " 13. Staurastrum furcigerum (a, 5-rayed: b, 6-rayed) x 350. " 14. Closterium griffithii, two sizes x 400. " 15. Cosmarium crenatum, N.Z. form x 400. " 16. Micrasterias rotata, N.Z. forms (a, sharp teeth: b, truncate teeth: e, end lobe x 350: d, comparative sizes N.Z. and English forms) x 200. " 17. Staurastrum gracile, N.Z. form x 400. " 18. Closterium acerosum (a, fronds with varying arms: b, the same with zygospore) x 90. " 19. Closterium selenæum, effect of glycerine x 60. " 20. Scenedesums acutus x 400 " 21. Holocystis (Tetrachastrum) incisa, abnormal x 200. " 22. Docidium clavatum, abnormal x 90.