BECENT RESEARCHES ON THE RESPIRATION OF PLANTS. 219 



The influence of temperature upon the respiration of plants is 

 not doubtful, for the Fagopyrum deprived of light, and at a 

 temperature of 35° C, gives out twice as much carbonic acid as 

 it does at the ordinary temperature of a summer's night. The 

 four examples just given serve not only to show the stimulating 

 action of heat on the respiration of plants, but they, or at least 

 the three first, may assist in determining the quantity of carbonic 

 acid exhaled and reduced. 



In short, as it has been found that the acid given off by a 

 plant in a confined atmosphere is wholly or partly reduced, it is 

 natural to admit that the three Fagopyra of the same weight, 

 and submitted for the same period of time to the same tempera- 

 ture, respired in the same manner, that is to say that they all 

 probably formed 120 cubic centimetres of gas, of which 78 cubic 

 centimetres were reduced by the first number, and only 54 by 

 the second ; the diflTerence of 24 cubic centimetres being, I 

 imagine, owing to the action of the baryta-water. This surmise 

 must not however be considered as a decided opinion, for it may 

 happen that in the dark all the acid produced by respiration is 

 completely given off, whilst under the influence of the solar rays, 

 whether direct or indirect, one part of the acid is reduced in the 

 parenchyma of the respiring organ. I am the more inclined to 

 think that this is often the case, because I have occasionally 

 observed that very small quantities of acid escaped reduction. 

 The means employed for ascertaining the reduction of acid 

 exhaled during the day may be also used for the purpose of 



