360 
PHYSIOLOGY. 
BOOK II. 
seed should be decarbonised by oxygen. This explains why 
Peas scarcely ripe will germinate much more rapidly than 
those which are fully matured; the former contain more 
pure water and less carbon. In fact, the effect of the ab- 
straction, by oxygen, of the fixed carbon, is, to bring back the 
seed to the state in which it was, before it was provided with 
the means of remaining unchanged in a torpid state. The 
sweet taste of germinating barley is, in reality, what the 
seeds possessed before they w'ere finally hardened. The 
destruction of oxygen, by the carbon of the seed, produces 
a sensible heat in germination, just as a similar cause pro- 
duces a similar effect in flowers, when the faecula of their 
disk is converted into sugar (seep. 331.). Hence the heat 
of masses of Barley which are made to germinate in dark- 
ness in order to become malt : and it can scarcely be 
doubted, that the change of the starch of that grain into 
sugar is chemically owing to the abstraction of a proportion 
of its carbon, and the addition of some other proportion of 
oxygen. 
It has been asked. Whence comes the oxygen which, com- 
bining with the carbon of the seed, forms the carbonic acid 
expelled in germination ? The usual answer is. From the 
air ; and it is necessary that seeds should have access to 
the atmosphere in order to germinate. But Messrs. Ed- 
wards and Colin have shown, by recent experiments, that 
the oxygen of which germinating seeds make use is ob- 
tained by the decomposition of water, and not necessarily 
from the air. These physiologists placed Beans in water, 
under such circumstances that they were completely cut off 
from access to the air. The Beans disengaged bubbles 
of air from their sides in great abundance for the space 
of 4 days, a part of such air collecting in a receiver, but 
the greater part dissolving in the water. This air consisted 
chiefly of carbonic acid ; there was also a trace of oxygen, 
and a small quantity of what appeared to be nitrogen. The 
hydrogen left after the decomposition of the water appeared 
to be absorbed by the seed, either wholly or in great part. 
This proof of the decomposition of water by the vital ener- 
gies of the seed is justly stated, by the authors now quoted. 
