NEW PUBLICATION. 81 



confirming the experiments which had been previously made in Eu- 

 rope. Under yellow light transmitted through a tube, so as to 

 exclude all extraneous light, decomposition of carbonic acid takes 

 place in the leaf.* When, however, a plant or leaf is exposed in 

 carbonated water to a violet ray, no such change ensues. Diges- 

 tion then in the leaf is promoted by the light of the solar beam, 

 and that kind of light which illuminates the most is also the most 

 energetic in promoting the growth of plants. For this reason in 

 part, vegetables growing in a clear bright sky, are greener and more 

 vigorous than those growing in a darker region or one fre- 

 quently overcast with clouds. The effect of light is seen by the 

 position which the growing branches always assume : in a green- 

 house, or in a pot standing in a window, they always direct them to 

 that quarter from which they receive the most light. The south 

 sides of trees in open fields grow the fastest upon that sde. The 

 rings of growth are thicker than upon the north side. Trees in a 

 forest produce their branches mostly at the summit. But light, 

 however, is not the sole agent in promoting a vigorous growth. 

 The presence of carbonic acid in the atmosphere, vapor, and tem- 

 perature, exert their share of influence. We do not, however, 

 subscribe to the doctrine that there ever was a period when a 

 greater amount of carbonic acid existed in the atmosphere, than at 

 the present. Admit this fact, and it would then be necessary to 

 admit another, viz., that the light of the sun was also greater, for, 

 by an increase of light only, could an additional quantity of car- 

 bonic acid be digested. For ourselves, we believe that the present 

 volume of the inorganic forces was established as early as the cre- 

 ation of organic beings. 



The twelfth and last chapter of Professor Draper's work, is " O71 

 the nervous agent in plants^ 



It is well known that in order that a being should possess sen- 

 sibility, it must be provided with a nervous apparatus or system, 

 and furthermore, in order that it may hold relations to the exter- 

 nal world, this system is equally necessary. Plants have not been 



• It is proper to add in regard to the effects of colored light, that [they do not 

 seem to be sustained by experiments reported in the Journal of the Franklin Institute, 

 where yellow light appeared to destroy, or at least injure, the vitality of seeds. In 

 the experiments referred to, the blue and green rays appeared to exert the least favor- 

 able influence on seeds, and the young plants which were produced from (hem. — Eds. 



VOL. I. — NO. 1. L 



