OF LIFE, AND ITS CONDITIONS. 31 



the expense of carbonic acid, water, and ammonia, various ternary and qua- 

 ternary Organic compounds, such as chlorophyll, starch, oil, and albumen; 

 and of the compounds thus generated, a part are appropriated by the con- 

 structive force of the Plant (derived from the heat with which it is supplied) 

 to the formation of new tissues; whilst a part are stored up in the cavities 

 of those tissues, where they ultimately serve either for the evolution of parts 

 subsequently developed, or for the nutrition of Animals which employ them 

 as food. Of the source of those peculiar affinities by which the components 

 of the Starch, Albumen, etc., 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 decomposition 

 of binary compounds seems to be a necessary antecedent of their formation, 

 it is scarcely improbable that as suggested by Prof. Le Conte, 1 that source 

 is to be found in the chemical forces set free in the preliminary act of de- 

 composition, in which the elements would be liberated in that "nascent con- 

 dition " which is well known to be one of peculiar energy. The influence 

 of Light, then, upon the Vegetable organism appears to be essentially ex- 

 erted 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 beyond 

 this. That the appropriation of the materials thus prepared, and their con- 

 version into organized tissue in the operations of growth and development, 

 are dependent on the agency of Heat, is just as evident in the stage of ma- 

 turity as in that of germination. And there is reason to believe, further, 

 that an additional source of Organizing force is to be found in the retro- 

 grade metamorphosis of organic compounds that goes on during the whole 

 life of the plant; of which metamorphosis the expression is furnished by the 

 production of carbonic acid. This is peculiarly remarkable in the case of 

 the Fungi, which being incapable of forming new compounds under the in- 

 fluence of light, are entirely supported by the Organic matters they absorb; 

 corresponding in this respect on the one hand with the germinating Plant- 

 embryo, and on the other with Animals. Such a decomposition of a portion 

 of the absorbed material is the only conceivable source of the large quantity 

 of carbonic acid they are constantly giving out ; and it would not seem un- 

 likely that the force supplied by this retrograde metamorphosis of the super- 

 fluous components of their food, which fall down (so to speak) from the ele- 

 vated plane of "proximate principles" to the lower level of comparatively 

 simple binary compounds, constitutes the power by which another portion 

 is raised to the rank of living tissue; thus accounting in some degree for the 

 very rapid growth for which this tribe of Plants is so remarkable. This ex- 

 halation of carbonic acid, however, is not peculiar to Fungi and germinating 

 embryos ; for it takes place during the whole life of Flowering Plants, both 

 by day and by night, in sunshine and in shade, and from their green as well 

 as from their dark surfaces. It is not improbable that, as in the case of the 

 Fungi, the source of this exhalation lies partly in the Organic matter ab- 

 sorbed ; Plants being able to take up and assimilate soluble humus, which, 

 being a more highly carbonized substance than starch, dextrin, or cellulose, 

 can only be converted into compounds of the latter kind by parting with 

 some of its carbon. 2 But it may also take place at the expense of compounds 

 previously generated by the Plant itself, and stored up in its tissues, of which 



1 See his very suggestive Memoir, On the Correlation of Physical, Chemical, and 

 Vital Force, in the Philosophical Magazine for 1800, vol. xix, Ser. iv, p 137. 



2 See the Memoir of M. Risler, On the Absorption of Humus, in the Bibliotheque 

 Universelle, N. S., 1858, torn, i, p 305. 



