890 JOUENAL OF THE ROYAL HORTICULTURAL SOCIETY. 



views on classification of these lower plants better than any existing 

 system. Turning now to the other primary group, the Diodees, we find 

 new terms proposed for Vascular Cryptogams on the one hand, and seed- 

 forming plants on the other. The latter, or Endoprothallees, are again 

 subdivided into newly-named groups corresponding generally with 

 Gymnosperms, Monocotyledons, and Dicotyledons. Whether the new 

 nomenclature will ever be adopted as a whole remains in the future, but 

 doubtless the principles of the system will play a part in the making of 

 any new classification. The author, in a criticism, indicates some of its 

 defects, notably the omission of those Fungi, the Bacteria, and the Blue- 

 green Algao, in which a sexual process is unknown. — W. G. S. 



Colourless Diatoms. 



Diatoms, Colourless. By G. Karsten {Flora, vol. Ixxxix. 1901, 

 pp. 404-433, pi. v.). — In many species the chromoplast diminishes in size 

 and fades when cultivated in nutritive solutions, even in adequate illumi- 

 nation. The colour and size of the chromoplast are restored when the 

 cells are removed to pure water. — M. H. 



Epidermis. 



Epidermis {BeiJi. Bot. Cent. bd. xi. ht. 4, pp. 219-258; plates 4). — 

 Herr Otto Damm gives a most interesting and instructive account of the 

 perennial epidermal layers found in Viscum and other plants. The 

 Viscoidece (Engler's classification) do not form cork except to cover acci- 

 dental wounds. Instead of cork a cuticular epithelium " is formed by 

 the external cells of the primary cortex. The epidermis itself persists for 

 a considerable time, and its cells both divid-e and also stretch sufficiently 

 to keep pace with the growth in thickness. An epidermal cell has been 

 seen with a tangential diameter of 120-130 micromillimetres, whereas at 

 the end of the first year the same diameter is usually 38 // ; the arched outer 

 cell-wall is sometimes 20 /.i in thickness. In certain Menispcrmacece 

 it was found that cork formation set in sooner or later, but after the above 

 " cuticular epithelium " had developed. In Acer and some nineteen 

 other plants it was found that only the epidermis cells themselves produced 

 a covering epithelium, and the primary cortex did not. 



The cuticular layers or outer cell- walls of the epidermis are not very 

 elastic, as they break at an elongation of between 2*8 to 5*1 per cent. 

 They possess considerable strength. That of Aristolochia broke at a weight 

 of lO'l kilograms per square millimetre, and an Acacia at 9*2 kilograms. 

 The paper is exceedingly instructive ; the work was done in the Botanical 

 Institute, Berlin University. — G. F. S.-E. 



Biology of Erysiphe^e. 

 Erysipheae, Researches on the Biology of the. Pt. I. By F. 



W. Neger {Flora, vol. Ixxxviii. pp. 333-370 ; pi. xvi., xvii.). — A study of 

 the modes of dissemination by the outgrowths of the perithecium and 

 their physical properties (hygroscopicity, &c.). — M. H. 



