178 PROCESS OF NUTRITION. CHAP. III. 



at the end of which he dried them as before, and 

 ascertained their weight also, which it was thus only 

 necessary to compare with the weight of the former 

 in order to know whether the plants had increased 

 in solid vegetable substance or not. But after many 

 experiments on a variety of plants, the result always 

 was, that plants when made to vegetate in pure water 

 only, and in an atmosphere of pure oxygene, or of 

 common air deprived of its carbonic acid, scarcely , 

 added any thing at all to their weight in a dried 

 state ; or if they did, the quantity was too small to 

 be appreciated. Particularly he made the experi- 

 ment on three plants of the Lysimachia vulgar is, 

 which he introduced into a receiver containing 250 

 cubic inches of common air deprived of its carbonic 

 acid, the roots were immersed in about one cubic 

 inch of distilled water, and the plants weighed in 

 their green state 129^ grains, displacing half a cubic 

 inch of their atmosphere ; three other plants of the 

 same species and weight when green, were found 

 to weigh when dried to a certain degree of the 

 thermometer and hygrometer 38J- grains: at the 

 end of eight days the plants which had been con- 

 fined in the receiver were taken out ; they had in- 

 creased considerably in length and were in a per- 

 fectly sound state, but had made no perceptible 

 change upon the atmosphere in which they vege- 

 tated either in purity or volume. They now 

 weighed in their green state J41 grains, but when 

 dried to the proper degree 40^- grains : they had thus 



