ZOOLO&Y AND BOTANY, MICROSCOPY, ETC. 617 



sunflower, pea, haricot-bean, scarlet-runner, cabbage, maize, wheat, 

 cucumber, and Trifolium Tiyhridum ; while, on the other hand, the lupin 

 and most woody plants contain but a very small proportion of nitrates. 



y. General. 



Volkens' Desert Flora.* — In his 'Flora of the Egypto-Arabian 

 Desert' Herr G. Volkens states a number of exceedingly interesting 

 facts respecting the means of protection of desert plants against excessive 

 evaporation, such as the storage of water in tissue especially adapted for 

 the purpose, a dense covering of hairs, unusual length of the root, &c. ; 

 and discusses the question whether transpiration is a physiological or a 

 purely physical process. 



Detmer's Laboratory Course of Vegetable Physiology.j — Prof. W. 

 Detmer publishes a very useful handbook for the use of practical students 

 in vegetable physiology. The methods of manipulation are, in particular, 

 described with great minuteness. 



Isotonic Coefficient of Glycerin. :|: — The isotonic coefficient of gly- 

 cerin has generally been assumed, in experiments on the plasmolysis of 

 cells, to be about 2, but without being founded on any definite observa- 

 tions. Herr H. de Vries has determined the point experimentally. 

 Tn the first place he was able to confi.rm Klebs's statement § of the 

 permeability of the protoplasm for glycerin, not only in the cells 

 of Zygnema, but also in Spirogyra, and in those of the violet epi- 

 dermis of the under side of the leaf in Tradescantia. But the per- 

 meability of protoplasm varies in different plants, in different cells of 

 the same plant, and probably also in the same cells at different periods 

 and under different external conditions. As the result of a series of 

 experiments de Vries found the isotonic concentration of potassium 

 nitrate, as compared with that of glycerin, to be, on the average, 0*592, 

 and the isotonic coefficient of glycerin to be 1 • 78. The following are 

 the coefficients for other substances : — cane-sugar, 1 • 88 ; invert-sugar, 

 1 • 88 ; malic acid, 1 • 98 ; citric acid, 2 • 02 ; tartaric acid, 2 • 02. 



B. CRYPTOGAMIA. 



Cryptogamia Vascularia.' 



Oophyte of Trichomanes. ]| — Prof. F. O. Bower describes certain 

 normal and abnormal developments of the oophyte of Trichomanes 

 pyxidiferum and alatum. 



In the former species the spores germinate freely while still within 

 the indusium, or even in the sporangium, developing a much-branched 

 filamentous protonema-like prothallus, not unlike a Vaucheria to the 

 naked eye, resembling the protonema of a moss, but coarser ; the fila- 

 ments are partitioned by septa into somewhat barrel-shaped cells. This 

 prothallus is frequently an aposporous growth, derived from imperfect 

 sporangia arrested in their growth, or even from cells of the columella. 

 The antheridia are produced laterally on the prothallus, either singly or 



* Volkens, G., ' Die Flora d. agyptisch-arabischen Wiiste,' 156 pp. and 18 pla. 

 Berlin, 1887. See Flora, Ixsi. (1888) p. 25. 



t Detmer, Dr. W,, ' Da^ Pflanzenphvsiologische Prakticum,' Jena, 1888. 



1 Bot. Ztg., xlvi. (1888) pD. 229-3.'5, '245-53. 



§ See this Journal, 1887, p. 440. || Ann. of Bot. i. (1888) pp. 269-305 (3 pis.).' 



