986 RECORD OF CURRENT RESEARCHES RELATING TO 



reported,* M. Cauvet now adds the following as definite conclu- 

 sions : — 



1. The roots of plants are constantly disengaging carbonic acid. 



2. This exhalation is less active by night than by day. 



3. The disengagement increases at sunrise, diminislies towards 

 the middle of the day, and increases again in the evening. 



4. The exhalation is, in proportion, more considerable during any 

 one diurnal period than during the night. 



5. The activity of the roots is hence less by night than by day, at 

 least as respects their respiration. 



6. If the root absorbs carbonic acid from the soil, it is possibly 

 only that which has served for the dissolution of the insoluble salts, 

 carbonates, phosphates, &c., necessary to the life of the plant. 



Digestive Principles of Plants.f — Dr. Lawson Tait has recently 

 investigated afresh the digestive principles of plants. While he has 

 obtained complete proof of a digestive process in Ceplialotus, Nepenthes, 

 Dioncea, and the Droseracese, he entirely failed with Sarracenia and 

 Darlingtonia. The fluid separated Irom Drosera hinata he found to 

 contain two substances, to which he gives the names " droserin " and 

 " azerin." 



Dr. Tait confirms Sir J. D. Hooker's statement that the fluid 

 removed from the living pitcher of Nepenthes into a glass vessel does 

 not digest. A series of experiments led him to the conclusion that 

 the acid must resemble lactic acid, at least in its properties. The 

 glands in the pitchers of Nepenthes he states to be quite analogous to 

 the peptic follicles of the human stomach ; and when the process of 

 digestion is conducted with albumen, the products are exactly the 

 same as when pepsine is employed. The results give the same reac- 

 tions with reagents, especially the characteristic violet with oxide of 

 copper and potash, and there can be no doubt that they are peptones. 



Nutrition of the Drosera.| — Contrary to the views of Reess and 

 Darwin, E. Regel finds that the plants thrive best when not treated 

 with animal food, and is of opinion that their sustenance is properly 

 derived through the roots. 



Botanical Micro-Chemistry.§ — In a Danish work on this subject, 

 V. A. Poulsen gives a resume of the most important micro-chemical 

 reagents, and the modes of investigation employed in micro-chemistry. 



The first section treats of the reagents. In each case the composi- 

 tion is given, and the cases in which each reagent should be emj^loyed, 

 and its characteristic reactions. The second section treats of vegetable 

 substances, and the methods of proving their presence by the aid of 

 micro-chemistry. Among the substances thus discussed are cellulose, 



* See this Journal, ante, p. 665. 



t ' Proc. Birming. Phil. Soc.,' i. (1880) pp. 125-39. See ' Nature,' xxii. (1880) 

 p. 521. 



X 'Journ. Ohem. Soc.,' Abstr. xxxviii. (1880) p. 820; from 'Bied. Centr.,' 

 1880, p. 482. 



§ Poulseu, V. A., ' Botanisk Mikrokemie,' Copenhagen, 1880 (Danish). See 

 ' Bot. Zeit.,' xxxviii. (1880) p. .^26. 



