24 



with much certainty that plants are also nourished by the re- 

 ception of organic substances, and that the reception of these 

 as well as of inorganic substances, which are presented to the 

 roots in a dissolved state, is effected entirely according to the 

 fixed laws of physical forces. 



[By a long series of experiments it has been proved that 

 plants will not grow in a soil of inorganic substances ; if, how- 

 ever, organic substances be presented to them for nutrition they 

 vegetate, and fix in their green-coloured parts by the influence 

 of solar light the carbon from the carbonic acid of the air ; it is 

 chiefly the leaves which perform this function. After the fall of 

 the leaves they are converted into humus, and this again pre- 

 sents to the roots of the plant the necessary nutriment. REP.] 



M. v. Martius supposes that plants, in all the operations of 

 their vegetable life > act according to a certain law of preference, 

 therefore with that power which in the human mind becomes 

 will. The plants are thus said to choose from the manifold 

 nutritive substances at their disposal those to which they are 

 especially partial ; however, I am of opinion that ah 1 correctly 

 performed experiments, from which at least we must reason 

 until more recent ones shall have proved otherwise, tend to 

 show that vegetables cannot choose their nutriment. 



The Rev. J. B. Reade * has published several elementary 

 analyses, which would lead us to admit a very remarkable dif- 

 ference in the chemical composition of cellular membrane and 

 of spiral vessels in the same plant. The analyses were per- 

 formed in the laboratory of Mr. Rigg, but unfortunately the 

 method is not stated. Mr. Reade extracted from the roots 

 of the Hyacinth the spiral vessels from the surrounding cel- 

 lular tissue by rubbing them between the fingers, and then 

 both substances were subjected to separate analyses. He ob- 

 tained : 



Spiral vessels. 



Carbon 41-8 



Hydrogen .... 1*1 

 Nitrogen .... 4*3 



Water 51 -8 



Residuum . 1*0 



100 



Cellular tissue. 



Carbon 39'2 



Oxygen. ..... 7' 14 



Nitrogen .... 3' 9 



Water 48'5 



Residuum . TO 



100 



* On the Chemical Composition of Vegetable Membrane and Fibre. 

 Loncl. and Edinb. Philosophical Magazine, vol. xi. p. 421. 



