OUR PUBLIC SCHOOLS COLUMN

Otago Witness, Issue 3097, 23 July 1913, Page 72

OUR PUBLIC SCHOOLS COLUMN

FOR SENIORS AND JUNIORS. (Conducted by Magisxer, to whom all communications must be addressed.) [Magister will ho glad to receive Nature notes, marked papers containing educational articles, diagrams, details of experiments, etc., of scholastia interest to touchers and pupils. Correspondents must use o.vly oxe side of tho paper, and whether ’ using a pen name or not, must send both name and address.) THE WINTER GARDENS. In connection with a visit to tho Dunedin V inter Gardens, I am giving tho descriptions of orchids exactly as they appear in “Plant Biology" (3s 6d; University Tutorial Press) and in. ‘“Flowering Plants: Their Structure and Habitat” (2s 6d; Ailman and Son, Ltd.). Each supplements the other, and the latter is arranged under headings for teaching purposes. 0 RCHID A C E JE. (University Tutorial Press.) “The orchid family (ordhidacese) is characterised by an inferior one-chambered ovary and a zygomorphic petaloid peria/ith, which is frequently spurred. There is a single stamen, which is united with the style to form the ‘ column ’ in tho centre of the flower (fig. 108). Very high specialisation for cross-pollination has taken place in tho plants forming this order. This order consists entirely of herbaceous perennials. Our British sfiecies are all terrestrial, and commonly havo tubers in which food materials are stored up for next season’s flowering. These subterranean tubers usually consist of a swollen root with a bud attached to it, but many of tho epiphytic orchids which grow so commonly upon tropical trees have tubers which are stem-structures (■pseudo-bulbs’), and are of necessity above ground. The epiphytic forms have aerial roots, some oT which frequently hang freely downwards, and arc able to absorb moisture from the air, while others attach the plant to its support. Certain of tho roots of the Vanilla plant are short and act as coiling tendrils, while others grow downwatds and strike root in the soil. Many orchids—and especially the epiphytic forms —arc adapted to xerophytic conditions, and hence are able to grow in dry situations. Such forms often store up water in their swollen roots or stems. The inflorescence is a raceme, but the stalk of the flower is usually very short; the long inferior ovary makes a long flower-stalk unnecessary, as it pushes out tho flower and exposes the essential parts to visiting insects. The structure of tho ordliid flower is rather complex, but tho arrangements for croespo'lination are easy to understand if specimens of any species—e.g., tho common early purple orchis are carefully examined. In Orchis the three outer perianth-lobes (sepals) me similar in size and shape, but one of the inner lobes (petals) is very different from tho others. This large lobe (lubellum) is really the posterior one, but it is brought to the front of tlh© flowei by the twisting of the ovary. It consists of a broad lip and a spur in whoso wall honey is secreted. There is only one fertile stamen, which is carried up with tho stylo so as to stand above tho stigma, and it consists of two club-shaped organs,, the pollinia. Each of these consists of a mass of pollen-grains with a stalk, and the two pollinia arc joined below to a sticky gland. The latter adheres to the head or proboscis of bees in search of the nectar or succulent tissue at the bottom of tho spur, and the entire polliniutn is carried to another flower to whose stigma some or all of tho pollen adheres. Contact with the sligma is often assured by the fact that tho caudicle bends Torwards and downwards as it dries while attached to the bee’s head. Tho ovules develop, and are fertilised some time after pollination. Most orchids arc cross-pollinated by insects, but some have either cleistogarnous flowers, or open ones, which are usually se’f-polli-nated e*.g., bee orchid. Many, however, cannot be fertilised by their own pollen, and in a few cases tho latter even acts like a person There is great diversity among orchids in the structure of tho flower and the mechanism of pollination. Examine all the wild or cultivated orchids obtainable; tho commoner British orchids are orchis (several species), bee orchid, twayblado, butterfly orchid, bird’s-nest orchid (a saprophyte), lady’s tresses. After oxarailJr ing tho structure of an orchis—e.g. Early Purple, push a pointed pencil into the spur of the iabollum (to imitate the action of a bee thrusting in its longue to scrape the honeyed walls of the spur). Notice the two club-shaped masses of pollen which are withdrawn from their pockets and remain attached to the pencil by the sticky mass at the base of their stalks." ORCIILDACE.E. (Flowering Plants: Their Structure and Habitat.) This is a monocotyledonous order anct has the usual parallel veins and the floral loaves in whorls of three, Type: Early purple orchis (Orchis mascula). Rootstock : The underground stem each year forms a new tuber by the side of the decaying one of tho previous year. From this new tuber arises the stem of the following year. Leaves: Radical, rather broad, and often sjrottod. Inflorescence: A spike. Ficwers: Reddish purple, irregular, and cnigynous. Structure of flower: Perianth, 3 x 3. ’Flic outer whorl consists of three petaloid leaves, th© inner also of the same number. The largest leaf of the inner whorl forms a lower lip, and appears to bo on tho anterior side of the flower. It is prolonged into a spur, secretes nectar, and is called the labclluni. The peculiarity of tho structure of an orchid is that the androecium and gvnaeciurn are united to each other, the stamen being combined with th© style, forming what is called the column. Only one stamen is developed. The anther is twolobed, and tho pollen grains found in each anther-lobe arc united into masses, called pollinia. The best way to see this is to take a pencil with a sharp point and put it into the spur. The pencil must touch a little pouch-like organ exactly opposite the labollum, and projecting into the gangway of the nectary. This is the rofitoflum. Into this rostellurn the discs of the pollinia fit; consequently, as the pencil touches the rostcllum the pollinia adhere to it, and when the pencil is withdrawn one or both pollinia may bo seen on it. Each poilinium consists of a stalk, which bears the pollen masses, and at the opposite end it terminates in a disc, whidh fits into the rostellurn. Tho remaining stamens arc suppressed ; their position is indicated in the floral diagram. Judging from other monocotyledonous orders, the number of stamens would be six, and Darwin lias shown clearly that there are traces of six in the orchid. The gynsecium consists of three carpel*.

with three parietal placentae. The ovary ie twisted, and it is this that makes the true posterior side of the flower appear to he anterior. The style unites with the stamen, as mentioned above. Two stigmatio surfaces are easily seen just beneath and on each side of the anther; whilst it is considered that the rostellum, into which the discs of the pollinia fit, is a modified stigma. The fruit is a capsule, dehiscing by three valves. The seeds are small and light, and scattered by the wind. In the floral diagram it must be noticed that the parts of the flower are represented in their true positions, the labollum on the posterior side, t’he single stamen on the anterior, etc. Pollination : The labollum serves as a land-ing-place for the insect, which pushes its head into the chamber leading to the nectary. Projecting into this chamber is the rostellum. which must therefore be touched by the insect. As the insect touches the rostellum its outer membrane is ruptured, and the discs of the pollinia, which fit into the pouch of the rostellum, being sticky, adhere to the insect’s proboscis, and are carried to another flower. When the poilima are first removed from the anther they are eiect on the proboscis, but in the course of 30 seconds they fall through an angle of 90deg; so that by the time the insect roaches a second flower they are hanging down, and arc in- r.uch a position as to come in contact with the stigmatic surfaces on each side of flhe rostel'um, and thus the second flower is croes-pollinatcd. Were it not for this contrivance, the pollinia, would merely touch the anther of the fresh flower, and wou'd not cross-pollinate it at all. There is another provision of Nature that should be noticed: the stigmatic surfaces are sticky or viscid, but only sufficiently so to break the clastic threads which hold the po’lcn grains together. If they were more sticky the whole polliniurn would be pulled off from the insect ; but as it is, only a few grains are taken by each flower, so that one polliniurn can crosspollinate several flowers. Darwin found that the majority of orchids were crosspollinated. The bee orchid, however, pollinates itself. Tile chief points of difference in the structure of this spccioS are:—The anther opens of itself as soon as the flower is fully expanded, and docs not require any pressure on the rostellum to liberate the pollinia; then, owing to the stalks being very slender and flexible, when tho pollen masses fall out on the opening of the anther, the stalks hang freely in the air, and the pollen masses are in a position to strike the stigma. Darwin covered up a bee orchid with a net in order to prevent insects getting to the plant, and was able to watch the exact movements of the pollinia. These differences in structure account for the fact that the bee orchid pollinates itself. Genera: The largest British genus is Orchis, which includes several species, such as Early Purple, Spotted, Pyramidal, Marsh, etc. They a'l have a spur. The genus Habenaria, which includes among others, the butterfly and tho frog orchids, is also spurred. The butterfly is very sweet-sccntcd, and has particularly long spurs; the frog is green. The genus Opnrys differs from those just mentioned in having no spur. This includes the bee, the spider, and the fly orchids. The genus Nccttia, the bird’s-nrst orch’d, is so named from its rootstock, which consists of a dense mass of thick, rather succulent, fibres twisted in and out like a bird’s nest, it is pale brown in colour, and a very pood example of a saprophyte. The genus Cypripedium, or lady’s slipper, must be mentioned, as it has two stamens. It consists of a single British species, found only in Durham and Yorkshire. The genus Listera, tway-blade is easily recognised by its two broad ovate leaves, about sin from tlie ground. The other species, with small cordate icavrs. is a much more slender plant, belonging to mountain regions. Ecology: Orchids abound in the tropics, where they are generally epiphytic. Their aerial roots either adhere to the bark of the supporting tree, securing the plant in its '■'osition. or they may hang loose in the air.” METEOROLOGIOAL NOff'MS. All teachers, I think, should get the monthly meteorological report sent out by the director, if only to give illustrations showing the effects upon rainfall of the prevailing winds. • In May Wellington h id an unusual fall of 1160 points, of which 570 points fell in one day. Pretty heavy for Wellington, wasn’t iff But how docs that compare with in three minutes! The secretary of the Navy League in his lecture gives those figures for Panama—unusual, no doubt, but what a deluge while it lasted ! May records exceeding lOin wore: Waimatenui, 1048 points (North Cape to East Cape); Wekaweka (Cape Maria van Diemen to Cage Egmout), 1142 points; Tuumatatahi. Upper Waitotara, 1052 iioinrs; Pa-hau-tanui, 1245 points; Opau, North Makara, 1324 points (Eginont to Palliser); Brings. Mastcrton, 1250 points; Wainutu, 1201 points; Wainuiomata Reservoir, 2270 points; CSilverstrcarn, 1430 points; Stokes Valley, 1469 points; Ixnver Hutt, 1022 points; Karori Reservoir, 1118 points (East Cane to Capo Palliser); Bealey Flat, 1118 points (Kaikoura to Cape Saunders); Chatham Islands, 1049 points. The Hermitage came closp with 955 points, of which 754 points fell in one day. The record daily fall, however, goes to Wainuiomata with 995 points. How many tons to the acre is that? Mr Roberts says the fall at Ranfurly has been only 1107 points for the six months g°no; and another place has 90 per cent, of that in one day. Wyndhain South, too, records only 2.91 in for 24 days’ rain. Note Wairoa rainfall for June, 1909 and 1910. 1 think I have recommended “ Weather Science,” by R. G. K. Lcinpfort, M.A.. superintendent of the Forecast Division of the Meteorological Office, England, it is one of the sixpenny net People’s Boohs issued by T. C and K. C. Jack. He tells us that an inch a day is considered a heavy downfall ii the British Isles, and that the record is 8.03 hi. which fell at Suthwaite. in Cumberland, reputed to be the wettest spot in the is’onds. Its average is 139 in per annum. But what do you think of 55in. 29in ITin, and 3itt on four consecutive days—S9in. - the record for a t'phoon in the Philippines on July 14 to 17. 1911? The dominion men orologica! record 1 have been referring to—May -contains an interesting reference to the barometric and atmospheric conditions, so I am quoting it. Note the special reference to ike low barometer at the Bluff’ Atmospheric conditions won voty unsettled until .May 23. During this time barometric pressure was continuously below normal, and cold and boisterous weather prevailed generally. Tito Bay of Plenty and most parts of the NoVon province experienced somewhat milder conditions, being !es-s exposed to the cold and southerly winds. Ant icyclonic conditions prevailed towards the close of tko month, and the

usual accompanying fine weather, with cold and frosty nights, was experienced. Stormy weather was experienced in most parts on the let and 11th and over the South Island generally on the 20th and 21et, when the barometer recorded the very low reading of 28.48 in at the Bluff, which is only one-hundredth above th© lowest ever recorded in the dominion at mean sea-level. A cyclonic centre existed off East Cape between the Ist and 4th. and a- cyclone passed in sub-antarctic latitude on the 10th, while another passed through Cook Strait on the 11th. These were the chief causes of the unsettled weather prevailing about these dates. The total rainfall during the month, however, was not excessive, except in the southern portion of the North Island and parts of the east coast and southern districts of the South Island.” A question suggests itself here. What are the maximum and minimum barometrical readings recorded—corrected to sealevel, of course? Notes on our Records.—Notice 17deg of frost at Ranfurly, and that three times as much rain, and more, fell in one day in the Philippines as has fallen at Ranfurly in six months! Compare highest daily rainfall at Ranfurly and Wyndlham with that_ of Wellington. Compare Ross rainfall monthly and maximum daily with Ranfurly and Wyndham. Tawanui records give good comparisons, too. What is the coldest place in Otago? What is the minimum record for Otago? Ranfurly, July 1, 1913. Dear ” Mag.’ster,”—Th© following arc the meteorological records for the month of June: —Maximum temperature in screen, 57deg on the sth; minimum temperature in screen, 19dog on the 14th: minimum temporaure on ground, 15dcg on the 24th; average maxima in scre©n, 44.66 deg; average minima in screen, 26.9dcg; average minima on ground, 23.7dcg. Rainfall 95 points on six days. Maximum fall, 63 points on the Bth. Rainfall from January to date, 1107 points on 53 days. Frost occurred on 27 nights in the screen and on 28 nights on the ground.—Yours truly, A. W. Roberts Wyndhrm South, July 1, 1913. Dear “ Magister,’—The following are the meteorological records for the month of June: —Rainfall: On the Ist, .02in ; 2nd, .o"in ; 3rd, 02in; sth, ,21in; 6th, 30. n; 7till. ,02in; 6th, .18in ; 9th, .431 n; 10th, . 16in ; 11th, ,05in; 12th, .14in ; 13th, .02m; 14th, ,07m; 15th, ,34in; 16th, ,24;n; 17tli, ,02in; 18th, ,02in; 21st, .18in; 22nd. .02in; 25th, ,15in ; 26th, ,14in : 27th,- .04m ; 28th, ,03in ; 30th, .Olin- total, 2.94 in fur 24 days. Maximum ihermoftietcr, 53dog, on the 18th ; minimum thermometer, 31drg, on the Bth ; average maximum thermometer, 45.9 deg; average minimum thermometer, 36.9c1eg; average temperature at Ip.m., 44.2 deg. Wind on 30 days; prevailing wind from N.W. on 16 days. (Snow foil on the 6th—,sin (tlie fourth fall for the season), —and on the 9ilt— ,sln. Frost occurred on seven nights. — Yours truly, J. White. Ross Weather Record for Juno, 1913. Thermometer: 9 a.m. Maximum, 54deg ; minimum 34dcg; mean, 43dcg; light---maximum, 46d g; minimum. 32deg; mean, 56Jeg; No. .32deg or under, 6. Barometer; Maximum. 31.32d0g; minimum, 29.67 deg; mean, 30.4 9i log. Rain; Total, S. 53 In; highest daily, 2.10 in; number of days, 15. Wind: 6, E., 2 N. Weather: Eighteen days bright, fresh, 12 days dull, cold, wot. — Yours truly, W. Winchester. ff’awanui School, July 7, 1913. Dear “ Magister,”—The fol’owing are the weather records for the month of June:—Hi guest temperature recorded, 72deg, on 4ih ; lowest temperature recorded, 29dcg. on 16th and 30th; number of nights temperature .32dcg or below. 12; average of maximum temperatur, s, 55.8 deg; average of minimum temperatures, 35.1 deg; average of barometric readings at 9.30 a.m.. 29 Bdcg; rah,fall, 2.37;n; number of days on which rain fell, 20; heaviest rainfa’l for 24 hours, 78in for the 24 hours ending 9.30 a.rn. on tlie 9ih. —Yours faithfully, J. G. Johnston. Wairoa. H. 8., July 7, 1913. Dear “ Magister,” —I regret that a vacation of three weeks, on account of teachers’ special physical culture classes in Napier, Ins prevented our records from being so full this month as 1 would have liked. Rainfall, 3 82in on eight days; total for 1913 to June 30, ’.913. 17.51 hi on 61 days; total for corresponding period of 1912. 28.381 n on 72 days; June. 1907, 1.91 in; June. 1 803, 2.62;n; June, 1909. 50 points; June, 1910. 6 19:n ; June, 1911, 3.49iu; June, 1912, 10.23 in; June. 1913, 3.62 in; average for June, 4.137 in. Temperature: Minima, 33d: g on 2nd and 30th ; maxima. 73drg. on 4th. — 1 am, etc.. John Bowie, Headmaster.