836 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Three methods are given for separating the result of the action of 

 chlorophyll from that of respiration. One is by calculating the 

 difference between the whole amount of gas emitted and absorbed by 

 plants exposed to light, and the volume which they emit by respira- 

 tion alone in the same light. A second method consists in suppress- 

 ing assimilation by the use of chloroform or ether without altering 

 the respiration. In the third method, two plants, of which the 

 physiological identity has previously been ascertained, are exposed, 

 the one to ordinary air, and the other under similar conditions except 

 that a concentrated solution of barium hydrate is placed in the con- 

 taining apparatus to absorb the carbonic acid formed. Under these 

 circumstances an excess of oxygen is found in the apparatus without 

 baryta, while in the apparatus containing it the carbonic acid when 

 set free by hydrochloric acid is found to be in excess of that in the 

 other vessel. The conclusion arrived at by the authors from these 

 experiments is that the volume of oxygen disengaged by assimilation 

 is greater than that contained in the carbonic acid decomposed.* 



Respiration of Plants at different seasons.f— MM. G. Bonnier 

 and L. Mangin give the following experimental results on this 

 subject : — In any given stage of development, the proportion between 

 the volume of carbonic acid given out and that of oxygen absorbed, is 

 constant, whatever the temperature. This proportion remains also 

 constant if the pressure of oxygen is diminished, and that of carbonic 

 acid increased. 



Galvanotropism of Roots.J — Herr J. Brunchorst describes under 

 this name the curvature in roots growing free in water caused by a 

 galvanic current. Weaker currents cause curvatures which are con- 

 cave on the side of the negative electrode; these he calls negative 

 curvatures ; while stronger currents cause curvatures which are 

 concave on the side of the positive electrode ; and these he calls 

 positive curvatures. The point of passage from negative to positive 

 curvatures varies greatly with different plants. Decapitated roots 

 exhibited only positive curvatures. 



Movement of Water in Plants.§ — In support of Godlewski's view 

 as to the cause of the ascent of water in plants, || Herr J. M. Janse 

 describes the following experiment. The central portions of long 

 branches with abundance of leaves at their summit were placed in a 

 water-bath without separating them from the plant. The portion im- 

 mersed in water, from 15 to 20 cm. long, was heated for an hour to a 

 temperature of 70° C. The result was that in Fudtsia glohosa the 

 leaves above the heated part began to wither the next day, and after 

 five days were completely dried up. Syringa vulgaris held out some- 

 what longer, its leaves did not begin to wither till the fifth day, and 

 were all dead in seventeen days. He concludes that the co-operation 

 of the living elements of the wood is essential for the ascent of water 



* See Bull. Torrey Bot. Club, xii. (1885) pp. 63-4. 



t Bull. Soc. Bot. France, vii. (1885) pp. 175-80. Bee tliis Journal, ante, p. 679. 



X Ber. Deutsch. Bot. Geseil., ii. (1884) pp. 204-19. 



§ Maandbl. v. Natuurwet., 1885, pp. 11-24. See Bot. Ztg., xliii. (1885) p. 302. 



II See this Journal, ante, p. 490. 



