General Notices. 181 



unusual coldness in any summer month, in producing a similar degree of 

 unusuid warmth or coldness in its corresponding winter month, more apparent 

 than could have been anticipated." (Alhenceuni.) 



Some interesting remarks in accordance with this paper will be found in 

 Pouilliet's Essay on Terrestrial Heat. — Cond. 



Respiration of Plants. — M. Colin has read before the Academy of Sciences 

 a memoir on the respiration of plants, the experiments detailed in which were 

 performed with M. Edwards, sen. 



Scarcely any of the phenomena of the respiration of plants have been 

 hitherto recognised, except the disengagement of carbonic acid gas ; and this 

 has been explained by the combination of the oxygen of the air with the 

 carbon of the grain. Thus, according to this theory, the grain is only acted 

 upon by the atmosphere, and the action of water on the respiration of plants 

 is not considered. In the respiration of leaves, carbonic acid is evolved 

 during the night, and during the day it is absorbed, and oxygen is disengaged 

 by the direct solar rays ; and these facts are explained on the supposition 

 that the carbonic acid absorbed is decomposed by the plant, its carbon appro^ 

 priated, and the oxygen disengaged. But this explanation supposes the plant 

 to possess a decomposing power, which to MM. Edwards and Colin it seems 

 difficult to admit ; and they have in consequence resumed the examination of 

 this function of plants. 



Hitherto the experiments performed on the respiration of grain have always 

 been performed in the air ; or when they have been performed in water, the 

 explanation of the phenomena have been limited by what occurs in the air : 

 what has been disengaged in the fluid has not been examined ; but this has 

 been done by MM. Edwards and Colin. 



They took a globe with a straight neck, the capacity of which was from 

 three to four litres of water (about 183 to 244 cubic inches), with which it 

 was filled ; and they then introduced forty large and perfect Windsor beans 

 (feves de marais). To the globe a bent tube was adapted, and which termi- 

 nated in ajar also filled with water. The beans were then in contact only with 

 the water and the air which it contained, and which could not be renewed 

 on account of the mode in which the experiment was performed ; and this 

 is an important circumstance, and upon which the success of the experiment 

 depends. 



The first phenomenon which appeared was the disengagement of bubbles of 

 air arising from the seeds : at the end of twenty-four hours the disengagement 

 Vv'as considerable. At the expiration of four days the beans were weighed ; 

 they had increased twenty per cent in weight. When put into the ground, they 

 came up perfectly ; which proves that they had suffered no change. As to the 

 production of gas, that which was disengaged, after passing through the water 

 and received in the tube and jar, was only a sign of tlie function ; it could be 

 only that portion which the water did not dissolve as it was gradually formed, 

 it was therefore smaller in quantity than that which was dissolved. The 

 quantity of air which had passed through the water without being dissolved* 

 amounted to from twenty to forty millimetres (I '22 to 2*44 cubic inches) ; 

 but that which was dissolved in the water, and which was expelled from it by 

 ebullition, was very considerable. Before this experiment, the water in the 

 globe contained about 4'577 cubic inches of air ; and after the experiment 

 more than 30'5 cubic inches of gas were expelled. Thus the action of the 

 beans alone produced nearly 30 cubic inches of gas. No doubt, therefore, can 

 exist as to the action of water in the respiration of the beans. 



It was found that the gas generated consisted of, 1st, an enormous quantity 

 of carbonic acid ; 2dly, an almost infinitely small portion of oxygen ; and, 

 3dly, a very small quantity of a gas which appeared to be azote, or at any 

 rate the authors at present so consider it : its proportion was rather smaller 

 than that of the air contained in the water. 



These experiments, then, prove that during the respiration of plants water 

 is decomposed, and that the carbonic acid formed is derived from the oxygen of 



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