138 Prof. LeConte on the Correlation of Forces. 
plants should feed entirely upon elementary matter ; whereas ae- 
eording to the ordinary view of the direct conversion of light 
into organizing force, there is no reason why plants should not 
feed entirely on elements, except that one of them, carbon, is 
insoluble. 
4th. There are many other phenomena of vegetable life which 
receive a ready explanation on this theory. I have said that 
sunlight has the power of decomposing carbonic acid only in the 
green leaves of plants. Pale plants, such as the Fungi among 
eryptogams and the Monotropa among phenogams, have no 
power to decompose CO*. These plants, therefore, eannot feed 
upon chemical compounds—mineral matter. They must feed upon 
organic matter, which organic matter in its partial decomposition 
furnishes the force necessary for organization. If so, then this de- 
composition, as in the case of germination, must be attended 
with the elimination of CO*. Both of these are known to be 
facts. Pale plants do feed wpon organic matter and do evolve 
CO?. The necessary connexion of these facts with one another 
and with the principle of conservation of force, is now for the 
first time, as far as I know, brought out. The phenomena of 
nutrition in these plants is similar to that of seeds in germina- 
tion, except that the latter contain the organic matter already 
laid up within their own tissues, while the former derive it from 
decaying vegetable or animal matter taken ab externo into their 
tissues. In this case, too, as in germination, heat is apparently 
the physical force which effects the decomposition of the organic 
food, and which is therefore converted indirectly through chemi- 
eal into vital force. Light is actually unfavourable to this proeess ; 
for light tends to decompose, not to form CO*. In both eases 
therefore the conditions favourable for nutrition are, first, abund- 
ance of soluble organic matter, second, absence of light and 
presence of heat. This is, then, apparently the true reason why 
germinating plants and pale plants avoid the light. These plants 
grow by the oxidation of carbon and formation of CO*. Light 
decomposes CO?, and must therefore be antagonistic to its forma- 
tion, and consequently to the growth of these plants. Whether 
or not this property of light is entirely limited by the condition 
of its acting through an organic tissue, is a question yet unde- 
termined. Heat we know is fayourable to the oxidation of car- 
bon (combustion, fermentation, putrefaction, &c.) under all cir- 
cumstances. Has light an opposite property also under all 
eircumstances? or is this opposite property of light limited to 
the condition of its acting through the medium of an organism ? 
I hope the experiments already commenced, and still in progress, 
by my brother Prof. John LeConte, and published in the last 
“Proceedings’ and in the American Journal of Science and Arts, 
