1864.] Canrruntur on Correlation of Physical and Vital Forces, 85 
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, &c., are brought toge- 
ther, 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 (op. cit.), 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 the Vegetable organism appears 
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 beyond this. That the appropriation of the 
materials thus prepared, and their conversion 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 maturity as in that of ger- 
mination. And there is reason to believe, further, that an additional 
source of organizing force is to be found in the retrograde metamor- 
phosis of organic compounds that goes on during the whole life of the 
plant; of which metamorphosis the expression is furnished by the 
production of carbonicacid. Thisis peculiarly remarkable in the case 
of the Fungi, which, being incapable of forming new compounds under 
the influence of light, are entirely supported by the organic matters 
they absorb, and which in this respect correspond on the one hand 
with the germinating embryo, and on the other with Animals. Such 
a decomposition of a portion of the absorbed material is the only con- 
ceivable source of the large quantity of carbonic acid they are con- 
stantly giving out; and it would not seem unlikely that the force 
supplied by this retrograde metamorphosis of the superfluous com- 
ponents of their food, which fall down (so to speak) from the elevated 
plane of “proximate principles” to the lower level of comparatively 
simple binary compounds, supplies a force which raises another portion 
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 exhalation 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; and it 
is not improbable that, as in the case of the Fungi, its source lies 
partly in the organic matters absorbed ; recent investigations* having 
rendered it probable that Plants really take up and assimilate soluble 
humus, which, being a more highly carbonized substance than starch, 
dextrine, or cellulose, can only be converted into compounds of the 
latter kind by parting with some of its carbon. But it may also take 
* See the Memoir of M. Risler, ‘‘ On the Absorption of Humus,” in the ‘ Biblio- 
théque Universelle,’ N.S. 1858, tom. i. p. 305. 
