S^O On Fl-getafion^ 



Under such circumstances as totally precluded any contact 

 with vegetable earth) showed that plants vegetating in the 

 labove-mentioned mixtures^ perished after a whiles and iii 

 no instance survived a sufficient length of time to perfect the 

 parts of fructification. In fact, bulbs, cresses, and other plants, 

 which vegetate in water only, contain, after their growth, 

 rather less than the mean quantity of carbon that the origi- 

 nal bulbs or seeds contained before their devclopement ; and. 

 ■?\hatever carbon is contained in the leaves and branches 

 of such plants, it has been furnished and carried up into them 

 by the water as a vehicle ; yet allowing such plants only to 

 unfold their flowers, and no further. This is analogous 

 to what we observe in the animal kingdom^ as in eggs, 

 which contain within them a portion of nourishment ade- 

 quate to the life and growth of the embryo chick to a cer- 

 tain degree of perfection, beyond which it cannot exist or 

 increase without the administration of newly applied nutri- 

 ment. In like manrer, every seed contains within itself a 

 certain portion of the carbonic principle, Vvfliich, by the sole 

 aid of water, suffices to develop the young plant to a certain 

 point, beyond which it cannot increase without the con- 

 currence of fresh carbon. 



The attraction of the roots easily accounts for the in- 

 crease of water in plants ; and the decomposition of a part 

 of the water deposited within them, alike explains the in™ 

 crease of the hydrogen. The augmentation of their carbon 

 has been endeavoured to be accounted for by some philo- 

 sophers as arising from the decomposition of the carbonic 

 acid in the air : an opinion founded on the fact that oxygen 

 is disengaged from plants in the act of vegetation : and this 

 in greater proportion when watered with water impregnated 

 with carbonic acid gas. However this may be, the quan-. 

 tity of residuary carbon is not increased by the procesf? 

 mentioned j for plants reared in aerated water, afford on 

 analysis no more carbon than if otherwise circumstanced^' 

 So also the supposition of the oxygen disengaged in vege- 

 tation being derived from carbonic acid decon)posed by 

 the plant is erroneous ; for air long confined, night and 

 day, over plants, undergoes no change cither in volume or* 

 in goodness. And tlVis consequence ought naturally to 

 follow' from the exijeriraents of Ingenhouz, which show 

 that whilst vegetables are under the influence of solar light, 

 ihey give out oxygen ; but, when deprived of that influence, 

 they Take up the before disengaged oxygen, combine with 

 it a portiem of their carbon, and give oft' the carbonic acid 

 resulting from their uulon : and with respect to the disen- 

 gagement 



