576 



NATURE 



[October 4, 1906 



Pal;co2oic ferns were in reality seed-plants." Dr. Scott 

 showed, in his luminous address, that " a large body of 

 true ferns of a simple type — the Primofilices of Mr. .-Vrber 

 — existed in Carboniferous times," while it is probable that 

 true Marattiaceous ferns also existed side by side with 

 these. 



The second part of the discussion, dealing with the 

 formation of the well-known calcareous nodules found in 

 the coal seams of the Lower Coal-measures, though it 

 might be thought to be of purely technical and specialist 

 interest, is in reality of great importance to everyone con- 

 cerned with Palaeozoic botany, because the nodules in ques- 

 tion contain the greater part of the plant remains showing 

 histological structure that are known to us from Pala;ozoic 

 rocks, and their mode of formation is of the first import- 

 ance as throwing light on the question of how these plants 

 grew. Several geologists specially conversant with the 

 occurrence of Coal-measure fossils had been particularly 

 invited to take part in the discussion, which was an excel- 

 lent instance of the fruitful concentration of two branches 

 of science upon a special problem. Prof. Weiss opened the 

 discussion with a short general paper stating the problems, 

 and was followed by Miss Slopes, who gave an account of 

 her recent work, which went to show that the nodules 

 were formed in situ, the calcareous material being derived 

 by solution and re-segregation from marine shells the re- 

 mains of which are found in the roof of the same seam. 

 A possible chemical process by which such a solution and 

 re-deposition could be effected was indicated. The most 

 clinching proof of this method of formation was shown in 

 the case of two gigantic nodules lying side by side, in which 

 the petrified remains of plants are found to be continuous 

 from one to the other. It is clear that in such cases at 

 least the plant must have been petrified where it was 

 found. Mr. Lomax brought forward evidence which 

 seemed to him to support the rival hypothesis, that these 

 nodules were often carried by w^ater transport to the situ- 

 ations in which they were found. Mr. Watson, who has 

 worked with Miss Stopes, attacked the views of Mr. 

 Lomax, while Mr. Bolton, of Bristol, Prof. Hull, and 

 other geologists, including Dr. Teall, togk part in the 

 discussion. 



The second discussion took place in joint session with 

 Section D on Monday morning, .\ugust 0, and dealt with 

 the nature of fertilisation. The opening paper was given 

 by Mr. V. H. Blackman. This discussion is dealt with, in 

 the account of the proceedings of Section D (Nature, 

 September 27, p. 551). Here it need only be said that the 

 danger already referred to, that of choosing too wide a 

 subject for discussion, was to some extent apparent. The 

 work bearing on fertilisation is now so varied in kind and 

 occupies so many classes of workers, both zoological and 

 botanical, that it is difficult to focus the interest in a 

 single discussion. 



The third discussion was on the phylogenetic value of the 

 vascular structure of seedlings. Papers were read by Mr. 

 Tanslev and Miss Thomas, bv Mr. T. G. Hill, and by 

 Mr. A. W. Hill. Miss Sargant, Dr. Scott, and Prof. 

 Jeffrev took part in the discussion. The work of Mr. 

 Tanslev and Miss Thomas and of Mr. T. G. Hill to some 

 extent covered the same ground. In both cases the com- 

 parative anatomy of the vascular system of the hypocotyl 

 in Gymnosperms and Dicotyledons was the subject of 

 investigation. Mr. Tanslev and Miss Thomas found that 

 the type of symmetry of this structure had considerable 

 phylogenetic value, thus confirming and extending Miss 

 Sargant 's conclusion relating to Monocotyledons, published 

 some vears ago. Without going into technical details, it 

 mav be stated that nearly all the cases met with fall 

 naturallv into a series, and the conclusion is reached that 

 the more complex type, met with among the older Gymno- 

 sperms, and also among some Dicotyledons, is phylo- 

 genctically the older, while the simpler type, very widely 

 prevalent among Dicotyledons, is derived by reduction, 

 through various transitions, from this older type. Mr. 

 T. G.^Hill, while bringing to light many of the same facts, 

 was not in agreement with this view, basing his opinion 

 on the apparently primitive diarchy of the ferns. Mr. Hill 

 showed that the anatomical evidence pointed to the coty- 

 ledons of the " polycotyledonous " conifers being derived by 

 splitting, in some cases at least, from a primitive " dicoty- 



NO. 1927, VOL. 74] 



ledonous " type, a conclusion with which the joint authors 

 of the other paper concurred. 



Mr. A. W. Hill sought to show, by a consideration of 

 the seedlings of bulbous and rhizomatous species of 

 Peperomia and Cyclamen, that clues may be obtained to 

 the mode of evolution of the true Monocotyledons, the two 

 cotyledons assuming different functions. Thus in his view 

 the single cotyledon of the Monocotyledon represents only 

 one of the two cotyledons of the typical Dicotyledon, the 

 other being represented by the first foliage leaf. Miss 

 Sargant found herself unable to accept Mr. Hill's sugges- 

 tions. 



Several interesting papers on the vegetation of different 

 parts of the world were read. Mr. Seward communicated 

 a paper by Prof. H. H. W. Pearson, of Cape Town, who 

 is doing excellent work on the natural history of the in- 

 digenous Cycads. Mr. Hugh Richardson gave an outline 

 account of the vegetation of Teneriffe, laying stress on its 

 zonal distribution. Mr. C. E. Moss gave a general paper 

 on the succession of plant formations in Britain, in vt'hich 

 he dealt with succession from sand dunes, from salt 

 marshes, in lowland and upland peat formations, and in 

 certain types of forest, in all cases from his own observ- 

 ation. He used the term " formation " to mean " an 

 historical series of plant associations," beginning as an 

 " open " and ending as a " closed " association. .\ll these 

 papers were illustrated by lantern-slides. 



Palseontological papers of some importance were read 

 by Prof. Jeffrey, of Harvard, and by Prof. Weiss. Prof. 

 Jeffrey dealt with the structure and wound-reactions of the 

 Mesozoic genus Brachyphyllum, a genus of hitherto doubtful 

 aflfinity, which was now shown to be an undoubted member 

 of the .Araucarineffi, mainly from the evidence of recently 

 discovered material with the anatomical structure pre- 

 served. One of the most interesting points in the paper 

 was the use the author made of the " traumatic " resin- 

 canals found in Brachyphyllum. It appears that this plant 

 produced definite resin-canals in its wound callus like the 

 modern Abietinea?, and unlike the ancient or modern 

 AraucarincK. Largely, though not wholly, on this account 

 Prof. Jeffrey concludes that this old genus connects the 

 .'\raucarinea; with the .AbietinesE, removing the former 

 from their somewhat isolated position, and showing them 

 as undoubtedly coniferous. Mr. Seward, in the dis- 

 cussion, while recognising the validity of Prof. Jeffrey's 

 demonstration that Brachyphyllum was a member of the 

 Araucarineae. found himself unable to accept the evidence 

 of Abietinean affinity, and particularly that based on the 

 occurrence of the traumatic resin-canals. Dr. .Scott, on 

 the other hand, saw no reason w-hy such evidence should 

 not be valid. 



Prof. Weiss described an interesting new .Stigmaria 

 possessing a considerable amount of centripetal primary 

 wood, so that at first sight it has the appearance of a stem 

 of Lepidodendron, though its characteristic periderm with 

 the remains of rootlet cushions attached show that it is 

 undoubtedly of stigmarian nature. 



Dr. .\. F. Blakeslee described .some new results he had 

 obtained in connection with the " physiological sex " 

 which he discovered some time ago in the Mucorineje. In 

 Phycomyces nitens, in addition to the heterothallic spores, 

 homothallic mycelia may be obtained by special methods, 

 but the sexual character of these is unstable, and no fix- 

 ation of the homothallic character takes place. Dr. 

 Blakeslee 's paper was illustrated by a series of beautiful 

 preparations showing the homothallic and heterothallic 

 character respectively of various mycelia. The author also 

 contributed a general paper on differentiation of sex in 

 gametophyte and sporophyte. For the former he uses the 

 terms homothallic and heterothallic, for the latter homo- 

 phylic and heterophytic. Investigations are now proceed- 

 ing as to the sexual differentiation in the sporophyte of the 

 Bryophytes. The evidence shows that both " male " and 

 " female " spores exist in the sporogonium of ilarchantia 

 polymorpha, and attempts are being made to determine at 

 what point the segregation of sex occurs. Dr. Lang, Mr. 

 V. H. Blackman, and Mr. R. P. Gregory took part in 

 the discussion on these papers. 



Of purely physiological papers. Prof. W. B. Bottomley 

 contributed a verv interesting account of his successful 



