304 ANNUAL KECORD OE SCIENCE AND INDUSTRY. 



more readily than in the form of ammonia salts, favored the 

 growth of deep-rooted plants. Hence the herbage on plots 

 manured with nitrate of soda stood the drought much better 

 than that manured with ammonia salts. 



Source of the Carbon of Plants. 



The question as to the source of the carbonic acid from 

 which the carbon of plants is obtained, whether it is derived 

 exclusively from the atmosphere or partially from the soil, 

 lias been long discussed. Liebig was of the opinion that a 

 portion was obtained from the soil through the roots, while 

 Boussingault believed that the larger part, if not the whole, 

 comes from the air through the leaves. Experimental data 

 for the decision of the question have, however, been lacking. 

 Boehm, from experiments with the scarlet-runner bean, con- 

 cludes that young plants do not take up from the soil either 

 organic compounds or carbonic acid. He considers it not 

 improbable that the carbon of the carbonic acid decom- 

 posed by plants unites directly with water to form starch 

 {Ber. d. I). Chem. Ges., ix., 123). 



We have lately accounts of some very ingenious and in- 

 teresting experiments by Moll, from which the author derives, 

 evidently with good ground, several conclusions, of which the 

 resultant is that plants derive none of their carbon from 

 the carbonic acid imbibed from the soil through the roots 

 (Landw. Jahrb., 1877, vi., 327). 



Deherain and Vesque have made some very ingenious ex- 

 periments on the absorption and emission of gases by the 

 roots of plants, from which they conclude that (1) the pres- 

 ence of oxygen in the soil containing roots is necessary for 

 the existence of the plant ; (2) the root connected with the 

 stem evolves a quantity of carbonic acid less than the oxy- 

 gen absorbed ; (3) carbonic acid appears not to be derived 

 from the soil, and does not pass to the leaves in order to 

 build up proximate principles by its decomposition into car- 

 bon and oxygen (Comptes Mendus, lxxxiv., 959-9G1). 



On the whole, the latest experimenting very decidedly fa- 

 vors the belief that plants get all the carbonic acid from 

 which their carbon comes through their leaves, and none 

 through their roots. 



