151 
completed, germination as Bonnet and Sennebier ascertained by 
experiment, immediately stops. The food therefore is conveyed 
from the cotyledons into the radicle ; the radicle increases 
in size, assumes the form of a root, sinks down into the earth, 
and soon becomes capable of extracting the nourishment neces- 
seiry for the future growth of the plant. Even at this period, 
after the radicle has become a perfect root, the plant, as Senne- 
bier ascertained by experiment, ceases to vegetate if the coty- 
ledons be cut olf. They are still, then, absolutely necessary 
for the vegetation of the plant. The cotyledons now assume 
the appearance of leaves, and appear above the ground, forming 
what are called the seminal leaves of the plant. After this the 
plumula gradually increases in size, rises out of the earth and 
expands itself into branches and leaves. The seminal leaves 
soon after this, decay and drop otf, and the plant carries on all 
the processes of vegetation without their assistance. 
As it does not appear that there is any communication between 
the cotyledons and the plumula, it must follow that the nour- 
ishment passes into the plumula from the radicle; and accord- 
ingly we see that the plumula does not begin to vegetate till 
the radicle has made some progress. Since the plant ceases to 
vegetate, even after the radicle has been converted into a root, 
if the cotyledons be removed before the plumula is developed, 
it follows that the radicle is insufficient of itself to carry on the 
processesof vegetation, and that the cotyledons still continue to 
perform a part. Now we have seen already what that part is ; 
they prepare food for the nourishment of the plant. The root, 
then, is of itself, insufficient for this purpose. When the coty- 
ledons assume the form of seminal leaves, it is evident that 
the nourishment which was originally laid up in them for the 
support of the embryo plant is exhausted, yet they still continue 
as necessary as ever. They must therefore receive the nourish- 
ment which is imbibed by the root; they must produce some 
changes on it, render it suitable for the purposes of vegetation, 
and then send it back again to be transmitted to the plumula. 
After tlie plumula has acquired a certain size, which must be 
at least a line, if the cotyledons be cut off, the plant, as Mr. 
Bonnet euscertained by a number of experiments, afterwards 
repeated with equal success by Mr. Sennebier, does not cease 
to vegetate, but it continues always a mere pigmy : its size, when 
176 AUCTABICU. 
