ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 223 



diastase in the vegetable cell ; and the same effect is produced by 

 small quantities of organic acids as citric acid. The degree of acidity 

 of any particular part of a plant is constantly changing. He believes 

 also that the chief cause of the turgidity of the cell is the presence of 

 vegetable acids, which have the special quality of inducing endosmose, 

 and the presence of which greatly promotes the growth of the plant. 



Occurrence of Allantoin in the Vegetable Organism* — If 



branches of woody plants covered with buds are cut off and placed in 

 water until the buds unfold, the young shoots and leaves are found to 

 be rich in asparagin, formed most probably by decomposition of albu- 

 minoids. B. Schultze and J. Barbieri have undertaken a number of 

 experiments for the purpose of determining whether in these cases, in 

 addition to the amide, other nitrogenous substances are found. By a 

 similar treatment they obtained, besides asparagin, a highly nitro- 

 genous body, which appears to be identical with allantoin both in its 

 composition and in its reactions. This derivative of uric acid was 

 found in no inconsiderable quantity, amounting to from 0*5 to 1 • 

 per cent, of the air-dried substance. 



Excretion of Water on the Surface of Nectaries.! — Dr. W. P. 

 Wilson attributes this phenomenon to osmose, and not to any internal 

 pressure; a view which he supports by the fact that washing the 

 nectaries with water and then drying them with blotting-paper stops 

 the excretion. With regard to the influence of light on the excretion, 

 with some plants no effect was observed, while with others it was 

 greatly increased by direct sunlight. 



Determination of the Activity of Assimilation by the Bubbles 

 given oiF under water. t — Sachs proposed the method of determining 

 the intensity of the assimilation of water-plants by counting the number 

 of bubbles of gas given off in a certain time. To this plan the objec- 

 tion was made that the bubbles might be the result of some other cause 

 than assimilation. Dr. F. Schwarz has now confirmed the accuracy 

 of Sachs's method, by determining that the presence of carbonic acid 

 in the surrounding water is an indispensable condition to the giving 

 off of the strings of bubbles. 



Detmer's Vegetable Physiology. § — The 7th section of Schenk's 

 ' Handbook of Botany ' is occupied by a treatise on Physiology by 

 Detmer. The following are the subjects comprised in it : — Food- 

 materials of Plants, including the Process of Assimilation ; Origin of 

 the Proteinaceous Substances ; Composition of the Ash of Plants ; 

 Organic Compounds as Food-materials ; the Molecular Forces in 

 Plants ; the Movements of Gases ; the Absorption of Water ; the 

 Movements of Fluids ; the Absorption of Mineral Substances ; and 

 the Process of Metastasis. 



* Berichte der deutsch. cliemisch. Gesellsch., xiv. p. 1602. See 'Natur- 

 forscher,' xiv. (1881) p. 481. 



t Unters. aus dem bot. Inst. Tiibingen, i. (1881). See Bot. Ztg., xxxix. 

 (1881) p. 545. 



J Unters. aus dem bot. Inst. Tiibingen, i. (1881). 



§ W. Detmer, System d. Pflanzeupliysiologie, 1881. 



