ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 77 



the salicin in Salix alba, and the cafe in in Thea sinensis and Cola 

 acuminata. 



All of these glucosides or special compounds seem analogous to 

 sesculin, and, with the exception of daphnin, occur in the cells in com- 

 position with a tannic acid ; and M. Goris thinks it probable that many 

 of the compounds, both glucosides and alkaloids, occur in the plant 

 totally or partially combined with a body having the reactions of 

 tannin. It is these tanno-glucosides or tanno-alkaloids, very soluble 

 in water and alcohol, but also very unstable, which in the majority of 

 cases are the chief active principle in certain medicinal plants. 



Cyanogenesis in Plants.* — Wyndham R. Dunstan and T. A. Henry 

 have made a further contribution to this aspect of plant physiology, viz. 

 the isolation of Phaseolunatin, the cyanogenetic glucoside of Phaseolus 

 lunatus, an annual, widely cultivated in the tropics where the edible 

 bean is used as a vegetable. When a few beans are powdered and 

 moistened with cold water, the odour of hydrocyanic acid is perceptible 

 in a few minutes, but if boiling water is used, and the vessel is imme- 

 diately closed and allowed to cool, no prussic acid odour is perceptible, 

 and no evidence of its production can be obtained by the usual tests. 

 These observations indicate that the production of the acid is connected 

 with the action of an enzyme. The glucoside was isolated from an 

 alcoholic extract of the powdered beans, as spreading rosettes of colour- 

 less needles from \ in. to 1 in. long, which melt at 141° C. Its formula 

 was determined as C ]0 H n O 6 N, by combustions of specially purified 

 material dried at 100° C, and the correctness of the formula was con- 

 firmed by estimations of the dextrose produced on hydrolysis. The 

 alkaline hydrolysis proves that phaseolunatin is the dextrose ether of 

 acetone cyanhydrin. The hydrolytic enzyme of Phaseolus lunatus was 

 isolated as an amorphous white powder, almost completely soluble in 

 water ; it readily hydrolyses amygdalin, salicin, and phaseolunatin. As 

 the latter is also hydrolysed by the emulsin of sweet almonds, it is 

 probable that the enzyme of Phaseolus lunatin is emulsin. The occur- 

 rence in the plant, apparently throughout its life, of a cyanogenetic 

 glucoside, together with the enzyme appropriate for its hydrolysis, seems 

 to strengthen the view, previously expressed by the authors, that these 

 glucosides must play some definite part in the metabolism of plants. 



General. 



Australian Fossil Botany.f — R. Etheridge gives a description of 

 more complete specimens than have hitherto been obtained from the 

 Leigh Creek coal measures, South Australia, of Thinnfeldia odonto- 

 pteroides, and points out that the nervation is more complex than in the 

 typical form of the species, and that at least three varieties of nervation 

 have been included in Thinnfeldia : suggesting those of the three genera, 

 Thinnfeldia, Odontopteris and Lescuropteris. 



J. Shirley \ describes several new species, and gives notes on others, 



* Proc. Roy. Soc, Lxxii. (1903) pp. 2S5-94. 



t Contributions to the Palaeontology of South Australia, 1902, No. 12, p. 2(1 pi.). 



% Geolog. Survey, Queensland, Bull. No. 18 (1902) pp. 1-16 (11 pis.). 



