DYNAMIC FUNCTIONS OF PLANTS. 415 



The condition of the Plant which has attained a more ad- 

 vanced stage of its development, differs from that of the ger- 

 minating embryo essentially in this particular, that the organic 

 compounds which it requires as the materials of the extension 

 of the fabric are formed by itself, instead of being supplied to 

 it from without. The tissues of the coloured surfaces of the 

 leaves and stems, when acted on by light, have the peculiar 

 power of generating at the expense of carbonic acid, water, 

 and ammonia various ternary and quaternary organic com- 

 pounds, such as chlorophyll, starch, oil, and albumen ; and of 

 the compounds thus generated, some are appropriated by the 

 constructive force of the plant (derived from the heat with 

 which it is supplied) to the formation of new tissues ; whilst 

 others are stored up in the cavities of those tissues, where 

 they ultimately serve either for the evolution of parts subse- 

 quently developed, or for the nutrition of animals which em- 

 ploy them as food. Of the source of those peculiar affinities 

 by which the components of the starch, albumen, &c., are 

 brought together, we have no right to speak confidently ; but 

 looking to the fact that these compounds are not produced in 

 any case by the direct union of their elements, and that a de- 

 composition of binary compounds seems to be a necessary 

 antecedent of their formation, it is scarcely improbable that, 

 as suggested by Prof. Le Conte (op. ci.), that source is to be 

 found in the chemical forces set free in the preliminary act of 

 decomposition, in which the elements would be liberated in 

 that " nascent condition" which is well known to be one of 

 peculiar energy. 



The influence of Light, then, upon Vegetable organism ap- 

 pears to be essentially exerted in bringing about what may be 

 considered a higher mode of chemical combination between 

 oxygen, hydrogen, and carbon, with the addition of nitrogen 

 in certain cases ; and there is no evidence that it extends be- 

 yond this. That the appropriation of the materials thus pre- 

 pared, and their conversion into organized tissue in the opera- 



