6i6 



NA TURE 



[October 17, 1901 



Sections) on the teaching of botany, an account of which has 

 appeared in the report of the work of the latter Section. Mr. 

 A. G. Tansley described the vegetation of Mount Ophir and 

 gave a lantern exhibition of several photographs which he had 

 taken during a recent expedition to the Malay Peninsula. The 

 views of dense masses of Mafonia fectinata, Dipteris conjitgafa 

 and D. Lobbiana growing in the Mount Ophir region were 

 particularly striking as illustrating the present home of these 

 isolated fern genera which played a prominent part in European 

 vegetation during the Mesozoic epoch. Some excellent 

 botanical photographs from the Malay Peninsula were also 

 exhibited by Mr. Vapp, who acted for some months as botanist 

 to the Skeat Expedition. 



Thallofliyla. — Cytology of the Cyanophycece, by Harold 

 Wager. The researches of Scott, Zacharias, and others have 

 definitely revealed the fact that the contents of the cells of the 

 Cyanophycere are differentiated into two distinct portions, an 

 outer peripheral layer in which the colouring matters are placed, 

 and a central colourless portion which is usually spoken of as 

 the "central body." The central body is regarded by many 

 observers, and notably by Butschli, as a true nucleus. Accord- 

 ing to the author's observations, it appears to resemble the 

 nuclei of higher organisms, in that it is composed ol a chromatic 

 network, but it differs from them in the absence of a nuclear 

 membrane and nucleolus. Staining and other reactions show 

 that chromatin is present, but in most cases only in small 

 quantities. The presence of phosphorus in the central body 

 can also be demonstrated, as Macallum has shown, by means of 

 the molybdate phenylhydrazine reaction. In the process of 

 division the cell begins to divide and new cell-walls are formed 

 independently of the division of the nucleus. In the process of 

 nuclear division the chromatin threads become drawn out 

 longitudinally and parallel to one another, and are then divided 

 transversely. Some of the division stages, especially in elongate 

 cells, resemble stages in true karyokinetic division. 



The Bromes and their brown rust, by Prof. Marshall Ward, 

 F. K S. The author has been for some time occupied with the 

 grasses of the genus Bromiis and the behaviour of the Uredo of 

 the brown rust (Piiccinia dispersa) upon them. The plan of the 

 investigation includes the nature of infection and conditions of 

 attack, and all discoverable relations between host and parasite. 

 The germination of the grass seeds has led to interesting points. 

 They can be treated antiseptically in various ways and grown as 

 pure cultures in nutritive solutions in glass tubes of various shapes, 

 designed either to allow of the continuous aeration of the plantlet 

 by a current of filtered air drawn through by aspirators, or 

 not. 



Such pure cultures of the grass were then infected with uredo- 

 spores, and in ten to twelve days gave rise to pure cultures of 

 the Uredo, which germinated and infected other similarly pure 

 cultures of the grass inoculated with them. 



Long series of sowings were made to test the conditions of 

 germination of the uredo-spores. The minima and maxima 

 temperatures of germination were found to be about lo' C. and 

 27''5 C. respectively, the optimum being about i8° C. The 

 effects of light, of other organisms (e.g. Alga;), of various ex- 

 tracts, and of the age of spores, tVc. , were also examined. In- 

 fection experiments on pot plants were made — several hundreds 

 in all — on twenty-one species or varieties of Bromus. 



The general results are, put very shortly, as follows : — Al- 

 though the Uredo examined is in all morphological respecis ab- 

 solutely identical on all the species of Brotitus on which it occurs, 

 nevertheless if spores gathered from B. sterilis are sown on B. 

 mollis the infection fails, whereas spores of the same batch sown 

 on B. sterilis infect normally and rapidly. And similarly in 

 other cases. Spores from B. mollis readily infect B. mollis, and 

 (less certainly) its allies B. sccaliuus and B. vetutiniis, B. 

 arveinis And olhexs oi \.he Serra/alcus group ; but they fail on 

 B. tnaxtuuts, B. tectoruJii, B. sterilis, B. madriUnsis, iS;c. — 

 the Steiwbromus group — and so with other cases. 



These observations lend no support to either the mycoplasm 

 theory of Eriksson, or to any theory which attempts to explain 

 outbreaks of rust to intra-seminal infection handed down from 

 parent to offspring, and the author believes that the difficulties 

 hitherto met with in understanding the sudden epidemics of 

 these rust-diseases will disappear as we gain exact information 

 of the conditions of germination, infection, and incubation of 

 the disease-producing parasite ; as also of its habits of lurking in 

 the older leaves of the grass in spots where the production of 

 a very few spores — quite invisible on a casual overhauling of the 



NO. 1668, VOL. 64] 



grass — prepares the way for more extensive infection as the 

 weather changes. 



Prof Marshall Ward, F.R.S., communicated a paper by Mr. 

 T. Barker on spore-formation in yeasts, also an account, by Mr, 

 Howard, of a Diplodia parasitic on cacao and on the sugar- 

 cane. 



Pteridophyta. — Contributions to our knowledge of the game- 

 tophyte in the Ophioglossales and Lycopodiales, by WiUiam H. 

 Lang, (i) The prothalli of Ophioglossttm pendulum and ffel- 

 minthostachys zeylanica. The wholly saprophytic prothallus o 

 0. pendulum is at first button-shaped, but by branching the 

 older prothalli come to consist of a number of short cylindrical 

 branches radiating into the humus. The young prothallus and 

 the branches are radially symmetrical. In the older parts all 

 the cells except the superficial layers contain an endophytic 

 fungus. The prothallus is monrecious. The antheridia are 

 sunken, with a slightly convex outer wall one layer of cells 

 thick ; in surface view this shows a triangular opercular cell. 

 The neck of the archegonium, which projects very slightly, 

 consists of about sixteen cells in four rows. The central series 

 in all archegonia'yet observed consists of an ovum and a single 

 canal cell. A basal cell is present. The prothalli of Helmin- 

 thostacltys were found a few inches below the surface of the soil 

 in a frequently flooded jungle in Ceylon. The prothalli 

 are radially symmetrical. The smallest were stout cylindrical 

 structures the lower part of which was darker in tint and bore 

 rhizoids ; the upper bore the sexual organs, which arise acro- 

 petally behind the conical apical region. In prothalli which 

 bear archegonia the vegetative region is relatively more deve- 

 loped, and in both these and the male prothalli it becomes more 

 or less lobed. The antheridia are large and sunken ; the 

 slightly convex outer wall is two-layered except at the places 

 where dehiscence may occur, which consist of single large cells. 

 The archegonia have a neck, consisting of four rows of cells, 

 which projects considerably. 



(2) On the mode of occurrence of the- prothallus oi Lycopo- 

 diuin selago at Clova. The sporophyte of this plant is very 

 common on moors, screes and crags in the Clova valley, and in 

 these situations it seems to be reproduced almost entirely by 

 means of bulbils. On the sometimes submerged margin of 

 Loch Brandy, however, numerous sexually produced plants and 

 prothalli may be found growing in the soil between the stones. 

 The difference in the conditions under which the sporophyte can 

 exist and those necessary for the successful germination of the 

 spores is analogous to what has been found to be the case for 

 Helm inthostachys. 



(3) On some large prothalli of Lycopodium cernuum. The 

 prothalli of this plant, described by Treub, were of small size, 

 one of the largest measuring 2 mm. in height by i mm. across. 

 On the banks of roads close to Kuala Lumpur much larger 

 prothalli were found. They were cake-like structures, of a deep 

 velvety green colour, about 2 mm. in vertical thickness, but 

 measuring sometimes 6 mm. across : they were attached to the 

 soil by numerous rhizoids springing from the flat base. 



(4) On the prothallus of Fiilotmn. The prothallus of this 

 plant was searched for without success in Ceylon. The 

 sporophyte occurred en tree-fern trunks on Maxwell's Hill in 

 Perak, and a single prothallus was found there embedded among 

 the roots of a tree-fern close to a Psilotum plant. No other 

 plants grew on this tree-fern, and, although a few species of 

 Lycopodium occur sparingly in the locality, there seems a strong 

 probability in favour of this specimen being the prothallus of 

 Psilotum. The specimen measured one quarter of an inch in 

 height by -,'',■; inch across at the widest part. It consists of a 

 cylindrical lower region covered with rhizoids ; near the lower 

 end of this is a well-marked conical projection (primary tubercle). 

 The upper part widens out suddenly, and its thick overhanging 

 margin bears numerous antheridia. In general form the pro- 

 thallus resembles some small specimens of Lycopodium cernuum, 

 but the upper region, from which assimilating lobes are absent, 

 finds its closest analogue in prothalli of L. clavatum. 



Some observations upon the vascular anatomy of the Cyathe- 

 aceo;, by D. T. Gwynne-Vaughan. In a number of Dicksonias 

 with creeping or prostrate stems the vascular system is soleno- 

 stelic, the leaf-traces departing as a single strand curved into the 

 form of a horse-shoe, with its concavity facing towards the 

 median line of the rhizome — Dicksonia adianloides, cicutaria, 

 davallioides, apiifolia, and punctiloba. In Dicksonia rubiginosa 

 the vascular ring is interrupted by gaps other than those due to 

 the leaf-traces, and it may therefore be termed polystelic. In 



