146 BOTANY 



The mesozoic group of cycadophyta has become better known, and its range greatly 

 extended, the researches especially of Seward, Nathorst, Wieland and others have 

 served to show that the Williamsoniae were a very important and generalised group, 

 of which the Bennettiteae, which formerly loomed largely in our outlook over these 

 ancient forms, really only represented a somewhat specialised family. The strong 

 anatomical evidence adduced by Scott and others as indicating the affinities between 

 the Pteridosperms and Cordaitales of the palaeozoic period continues to receive, fresh 

 support, and the linking up of that ancient plexus with the more modern gymnosperms, 

 especially with the Cycadean alliance, has been made clearer by the investigations of 

 Oliver upon the structure of several important Pteridosperm seeds. 



Vascular Cryptoga-ms. In the domain of the Vascular Cryptogams the principal 

 accessions to recent knowledge have come from the palaeontological side. One of the 

 most important series of investigations is that of Kidston and Gwynne-Vaughan on 

 the fossil Osmundaceae, the general result of which has been to link up this group with 

 the palaeozoic primo filicean series. Considerable contributions have also been made 

 by P. Bertrand, W. T. Gordon and others to our knowledge of the anatomy of the ancient 

 Pteridophyta, and to some extent they tend to rehabilitate the importance of the 

 palaeozoic ferns. Furthermore, the brilliant discoveries of Count Solms have conclu- 

 sively demonstrated the true nature of the well-known and remarkable structure of the 

 Psaronius root sheath. One result of Count Solms' researches, however, is somewhat 

 to weaken the security of the foundations on which the ideas as to the systematic posi- 

 tion of this group have been built up. For further information on recent work on the 

 anatomy of fossil fern-like plants reference may be made to the excellent summary 

 given by P. Bertrand in the Progressus rei Botanicae, vol. iv (L'etude anatomique des 

 Fougeres anciennes et les problemes qu'elle souleve), where the modern literature is 

 fully cited. 



Fungi, Bacteria. Amongst modern advances of knowledge of the fungi perhaps the 

 chief point of interest is centred in the ascomycetes, concerning the fructification of 

 which the views are still very divergent. Claussen has recently adduced strong evidence 

 to show, in the forms studied by him, that no fusion of sexual nuclei occurs in the 

 ascogonium, but that the fusion which takes place in the young ascus is, as Dangeard 

 maintained, to be interpreted as the real sexual act. The cells of the ascogenous hyphae 

 contain two nuclei apiece, which may represent either morphologically, physiologically, 

 or both, the sexual nuclei which still remain separate but divide in pairs as they do in the 

 uredineae after the nuclear approximation has occurred in the hyphal cells. It is not until 

 the ascogenous hypha reaches its final stage, and bends over in the well-known hook- 

 like manner that nuclear fusion occurs. The penultimate cell is observed to contain two 

 nuclei, whilst the terminal one and the antepenultimate one have only received one 

 apiece. The ascus is formed from the binucleate penultimate, and the previously dis- 

 tinct nuclei which, though in juxtaposition, have remained separate in descent finally 

 fuse. This account is very different from that given by other competent investigators. 

 But it is alluring, and has been worked out with great skill. The matter urgently needs 

 to be settled as it affects not only our views as to the nature of the ascus, but also the 

 morphology and affinities of the whole of the ascomycetes to other groups of fungi. The 

 main lines of advance in the fungi myxomycetes and bacteria (apart from the physiology 

 of the latter) is along cytological lines. The last have been carefully studied by Dobell 

 (Quart. Journ. Micr. Sci., vol. 56, IQTI), who believes that they are all nucleated or- 

 ganisms, but that these nuclei may be of " chromidial " nature (I.e. granules scattered 

 through the cytoplasm) whilst they may be filamentous or of spherical form in other 

 species. It would seem that the actual nuclear character may differ in some of the 

 bacteria at various stages of the life history. 



The most recent studies of Jahn render it almost certain that reduction (meiosis) in 

 the myxomycetes occurs at spore formation. He adduces evidence to show that con- 

 jugation occurs during the initial stages of plasmodial formation, and when this has 

 occurred the new plasmodium treats the non-conjugated amoebiform myxomycete 



