W.E.A. CLASS IN BIOLOGY

Evening Star, Issue 19274, 12 June 1926, Page 9

W.E.A. CLASS IN BIOLOGY

DR HOLLOWAY'S LECTURE. Tho eighth of a scries of lectures of the W.K.A. class in biology vtur hold last ni"ht m tho Upper Oliver Room, University Buildings, llio lecturer being the Rev. Dr J. B. Holloway, P.H.Z.lnst.,'lecturer in LoUiny of the University of Otago. Dr Holloway, in his opening remarks, briefly referred to the, findings of previous lectures, showing that two types could be distinguished among existing spore plants—viz.: (1) Thoiso which have one kind of spore —this germinates into a free living prothallus (c.g., ferns, etc,); and (2) those which have two kinds of spores —namely, small male spores and larger female spores—these germinate into two corresponding kinds of male and female prothalli within the spores (selagineila and isoetes). The moat ancient fossil plants known were spore plants, some of which had one kind of spore, only, while others had two kinds. Of those latter some had proceeded further than had the modern Eolaginclla in the elaboration of the female spore into a “seed," and they must strictly bo, termed primitive seed plants. Th-o first land plants belonged to the lower Devonian epoch. Two of the few that were well known were called lihynia mid Hornca. The sporebearing stage was much mono simpy organised than in any other spore plants, whether fossil or modern, so niuo.li so that it could almost be likened to a marine alga (toawccd) which had taken to life half in and half out of Urn water. The spares wore borne in simple sporangia at the taps of the twigs. Tho game to-bearing stage or pro-l-hallus had not been found. These plants undoubtedly helped to bridge tho gap between the algai and Iho earliest land plants. 'The best known fossil plants of tho carboniferous epoch wore some of Hie chief trees and " troofern ” plants of the carboniferous forests (0.g., lepidodendron, sigillaria, calami tes, and the ptorido? perms). The organisation of the spore-bearing stage—that was, the * plant” itself —was very complex; so that hero they were a long distance away from the primitive land plants. Tho kpidodondrons ami cigillurias wore the ancestors of tho modem lycopodiums, salami up lias, and Lock's. Some had cones like those of lycopodium, with only one kind of spore. The prothallus of these species had not been found, and the chances were very much against it ever being foundSome had cones like those of selaginclla, with two kinds of spores, and prothallial tissno had been found in the larger female spores. In the case of others, again, sonic conoa had only female spores, and only one spore in each sporangium came to maturity. The important point in this latter case was that each of those spores was retained in its sporruimum, and that the sporangium itself became enclosed in a special envelope of tissue, so constituting a true seed. Tho pteridospernis were fernlilio Eocd'-boaring plants. Their male spores were borno in fern-like sporangia on some of the fronds, while each female spore in its sporangium and ouler envelope constituted a true seed. When the seed had reached maturity (bo outer envelope had dcvolopd into a fdmiy coat, with succulent “fruity” tissue as well. The catamites were tho ancestors of the modem oquiseturns. In summing up. Dr Holloway recapitulated tho principle points of tho lecture, emphasising that these fossil snore plants are of special interest for the following reasons: ill Soma of them suggest what, tho earliest laud plants wore like -. (2) they show, then, that the spore habit prcococd the seed habit in th® evolution of tho plant kingdom, and that tho ancestors of our modern relatively unimportant plants once covered the earth.; (J) the plordosporms represent, the ancestral stock from which oimic the modern cycads.