410 



KNOWLEDGE. 



October, 1910. 



laboratory, and who are too much disposed to regard work in 

 the field as waste of time. The horizon of the extreme 

 tvpe of " laboratory botanist " is apt to be bounded by 

 the walls of the laboratory itself, and it is time that 

 those responsible for the teaching of Botany in our 

 universities and colleges should do their utmost to discourage 

 the idea that the microscope, the microtome, and the other 

 apparatus of the laboratory, excellent as they are as aids to the 

 knowledge of plant-life, must not be allowed to monopolise the 

 student's attention and to replace thorough study of plants in 

 their habitats. The botanist's equipment is imperfect and 

 one-sided unless field work has throughout his training gone 

 hand in hand with regular outdoor observation all the year 

 round. 



Professor Trail de\ oted a large portion of his address to 

 criticism of the present literature of systematic and geographical 

 Botany in Britain, calling attention to the difficulties which 

 beset the path of those whose tastes lie in the direction of 

 studying plants in the field rather than in the laboratory, and 

 who wish to make as complete acquaintance as possible with 

 the plants of their own neighbourhood. He indicated some 

 of the more serious gaps in the literature of the British Flora 

 — using that term in the widest sense, instead of restricting it 

 to the vascular plants — and concluded with a plea for a well- 

 organised botanical survey of the British Isles. 



Space forbids a more detailed consideration here of 

 Professor Trail's valuable address, \otes are appended with 

 regard to some of the papers read in the Botanical Section. 



Professor Bower ("On two Synthetic Genera of Filicales") 

 dealt with two Fern types which on reinvestigation showed 

 structural characters of great importance in connexion with 

 the evolution of Ferns (Fihcales) and necessitating their 

 removal from the systematic position which they have hitherto 

 held within this group. As is well known. Professor Bower's 

 previous work has largely contributed to the establishment of 

 a more natural classification of the Ferns and of the whole 

 class of Ferns and Fern-allies iPteridophyta). He has shown 

 that the Ferns themselves fall into three series — Simplices, 

 Gradatae, and Mixtae — according to whether the sporangia in 

 each sorus arise simultaneously, in basipetal succession, or 

 in no recognisable order : the three series are further charac- 

 terised by a progressive diminution in the number of spores 

 produced by each sporangium, and by various other well- 

 marked features. Of the two Ferns specially dealt with as 

 ■■ synthetic " genera — linking up forms belonging to the three 

 series just mentioned — Plagiogyricj was previously classed 

 with Loiiiaria among the Mixtae, but in various respects (stem 

 structure, simple leaf-\ eining. absence of indusium, sporangium 

 with thick stalk and indeterminate stomium, and so on) it 

 shows resemblances to certain Simplices, especially to the 

 Schi^aeaceae, while its " mixed " sorus relates it to the 

 Pterideae among the Mixtae. It is suggested that Plagiogyria 

 represents a transitional form from the simple to the mixed 

 sorus. indicating that this step may have occurred without the 

 intervention of a gradate condition. A second and somewhat 

 similar sequence, leading, however, to the gradate series, starts 

 from the second synthetic genus, Lophosoria. a Tree-F'ern 

 formerly merged in the genus Alsophila. belonging to the 

 Cvatheaceae among the Gradatae. Here the sorus is of the 

 simple tvpe, but though this genus resembles the Gleicheniaceae 

 in many respects, the sporangium dehisces laterally instead 

 of vertically, and it is suggested that Lophosoria indicates 

 the beginning of a line of evolution which started from the 

 Gleicheniaceae and led to the Gradatae. By the help of these 

 two synthetic genera, Plagiogyria and Lophosoria. it is 

 possible to trace the origin of two great sequences, or 

 evolutionary series, of F'ems, along lines more or less parallel 

 but distinct — the one leading to the Pterideae section of the 

 Mixtae, the other to the Cyatheaceous type of Gradatae, and 

 it would appear that both may have arisen trom types of the 

 Simplices having affinities with the Schizaeaceae and 

 Gleicheniaceae. In working out the morphology of these two 

 interesting genera. Professor Bower has made an important 

 contribution towards the completion of his great classifica- 

 tion of the Ferns on a sound and natural basis. 



Dr. Kidston and Prof. Gwynne-Vaughan, in a paper on the 



fossil Fern genus Tciiipskya. described some specially well- 

 preserved Russian specimens which show that these fossils 

 consist of aggregates of branching fern stems imbedded in a 

 compact mass of their own interwoven adventitious roots. 

 The " false stems " thus produced no doubt grew erect as 

 columnar or conical structures about nine feet high, the 

 individual stems being only about the thickness of a slate 

 pencil. Strangely enough, though growing erect, the plant 

 shows well-marked dorsiventral symmetry, having all the 

 leaves on one side of the stem and the roots on the other. 

 The existence of a Fern with this peculiar habit of growth 

 suggests that the strong erect arboreal stems of the modern 

 Tree-Ferns may not be a primitive feature of the order, and 

 these plants may have been derived from forms with a 

 rc';)(^s/o3'(7-like habit, in which the original axis has so 

 greatlv surpassed its branches in size and importance that the 

 latter are now almost entirely suppressed, with the result that 

 we have now in the Tree-Ferns of to-day a single main axis 

 strong enough to grow erect without the additional support of 

 a mantle of roots. 



As regards the Gynmosperms, we may note an interesting 

 paper bv Mr. M. G. Thoday on the ovule of Gnetiitn 

 africaiunu. In the young ovule the three coverings arise 

 together at the base of the nucellus, the greater portion of 

 the latter standing free in the centre of the ovule. During 

 later development the region between the two inner coverings 

 becomes more and more stretched, so that the innermost 

 covering arises near the apex of the nucellus. and the free 

 portion of the nucellus in the mature seed is \ery small in 

 proportion to the part developed by intercalary growth. The 

 outer covering resembles the bracts in structure, and is 

 regarded as an extra covering, while the two inner are called 

 integuments and compared with the two integuments in 

 \Vcl\cifschia. The middle covering (outer integument) has 

 well-developed vascular bundles, while those of the inner are 

 feeblv developed. .\ large pollen-chamber is present in the 

 voung ovule. The radial structure of the seed, the presence 

 of a pollen-chamber, and other characters mark Gnetum otf 

 very sharply from Weliicitschia, and probably point to the 

 more primitive nature of the Giictnin ovule. The two 

 integuments in both seeds are compared with those of 

 Lagcnostoma (the seed of Lygiiiodeiiilroii, one of the 

 remarkable " Pteridosperms " which form a connecting-link 

 between Ferns and Gynmosperms). the vascular supply of the 

 inner integument having suffered great reduction. 



Of the remaining papers here noted, the majority dealt vv ilh 

 phvsiological topics. Dr. F. Darwin described a new method 

 of observing stomata. by means of an instrument devised by 

 him and named the " Porometer." The apparatus consists of 

 a small glass chamber which is cemented on to the stomatal 

 surface of a leaf and connected with a suction-tube and 

 manometer. By diminishing the air-pressure within the 

 chamber, an air-current is made to flow from the leaf through 

 the stomata into the chamber, the diminished pressure in the 

 intercellular spaces leading in the same way to a flow from the 

 external air into the leaf. In practice it is found that the rate 

 of air-flow is strikingly under the influence of the conditions 

 which are known to aftect the aperture of the stomata. Thus 

 at night the rate diminishes greatly, and the same effect can be 

 produced by artificial darkness or by severing the stalk and 

 allowing the leaf to wither. When the rate of air-flow is 

 compared with the loss of weight by transpiration, it is found 

 that the two curves rise and fall together, but the Porometer 

 readings have a much greater range than the record of 

 transpiration. It is found, however, that when the Porometer 

 curve is constructed from the square roots of the rates of 

 flow, it is roughly parallel to the curve of loss of weight. This 

 is what we should expect, for Dr. H. Brown has shown that 

 diftusion through a plate pierced by small apertures is 

 proportional to their linear dimensions, while on the other 

 hand the flow of air through such a plate must vary as the 

 area of the holes. 



Mr. S. Mangham described some results of his reinvestiga- 

 tion of the paths taken by sugars during translocation from 

 the leaves of green plants. Haberlandt and Schimper con- 

 cluded, from their anatomical and microchemical researches, 



