RECENT RESEAKCHES ON THE KESPIEATION OF PLANTS. 



221 



Names of Plants. 



Weights. 



Acid 

 exhaled. 



Observations. 



1. Fagopyrum cymosum .... 



2. Fagopyrum cymosum .... 



3. Syringa vulgaris (2 young shoots) 



4. Kitaibelia vitifolia 



22 

 22 

 22 

 22 



c.c. 

 7-5 

 7-5 

 8-0 

 10-0 



I The mean tempe- 

 rature rose to 

 17°'5C. 



In order to complete the experiment the four apparatus were 

 got ready, the next day, at the time at which the eclipse had oc- 

 curred, and in them were placed other specimens of the same 

 plants and of, as nearly as possible, the same weights as those 

 before used. The sky was clear and cloudless, and the tem- 

 perature average, but in the shade 2° C. higher than before. 



Names of Plants. 



Observations. 



1. Fagopyrum cymosum .... 



2. Fagopyrum cymosum .... 



3. Syringa vulgaris (2 young shoots) 



4. Kitaibelia vitifolia 



In the shade. 

 In the shade. 

 In the sun 2 hours. 

 Ditto. 



From the above it would seem that the eclipse of the 28th of 

 .July had no sensible influence on the respiration of plants, and 

 that the smaller quantity of carbonic acid existing when the 

 eclipse was over ought to be attributed to the lower temperature 

 caused by the interception of the sun's rays by the clouds, inas- 

 much as in the experiments made the next day the difference was 

 greater, as the temperature to which the apparatus was exposed 

 was greater. However, it may be concluded that the temperature 

 being the same, tlie acid expired would have been more abundant 

 in the diffused light caused by the eclipse ; for the reduction of 

 the acid gas is known to be much less intense in the ordinary 

 light of day than in the sun. 



If it be inquired how M. Theodore de Saussure, whilst en- 

 gaged in his experiments on the respiration of plants, happened 

 to overlook the fact that carbonic acid is given off by them, it 

 can only be answered by way of conjecture that in all proba- 

 bility he was so intent upon its decomposition by the leaves when 

 acted upon by the sun, and upon the importance of tliat gi-eat 



