108 GERMINATION OF SEEDS: SEEDLINGS 
cotyledons. Thus most of the stem and all of the leaves, flowers, 
and fruit of the adult stage are produced by the plumule. 
The cotyledons, which are commonly fleshy in these seedlings, 
enlarge after reaching the light and their color changes to 
green, which with the presence of stomata indicates that they 
function to some extent like ordinary leaves in the manufacture 
of foods. However, it 
is only a short time till 
most of them, espe- 
cially the fleshy ones, 
begin to show shrink- 
age which continues as 
the food is used for 
growth, until much 
shriveled and dried 
they fall from the 
plant. In some cases, 
as in the Buckwheat 
and Castor Bean where 
the seeds are albumin- 
ous, the thin cotyledons 
are more leaf-like and 
function like ordinary 
leaves for a consider- 
able time, although in 
arrangement, shape, or 
size they are never just 
like ordinary leaves and 
never so long-lived. 
. (Fig. 102.) Where the 
Fia. 102. — Seedling of Castor Bean, in which aled 1 
the cotyledons persist and function like leaves bial acct anG sauces 
for some time. much force is required 
to pull them through 
the soil, and, consequently, when the ground is hard or covered 
with a crust, seedlings of this type often fail to develop. 
As to how the development of both radicle and plumule pro- 
ceeds until the adult stage is reached, that depends much upon 
the kind of plant. In most cases the radicle forms a central root 
which, although prominent at first, may be much obscured in the 
adult stage by large secondary roots developing from the base of 
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