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SEED. 
Cotyledons , (from a Greek word kotule, a cavity) are 
the thick fleshy lobes of seeds, which contain the embryo. 
In beans they grow out of the ground in the form of two 
large leaves. They are the first visible leaves in all seeds, 
almost always fleshy and spongy, of a succulent and nour- 
ishing substance, which serves for the food of the young 
plant at the moment of its germinating. Nature seems to 
. have provided the cotyledons to nourish the young plant in 
its tender infancy. After seeing their young charge suffi- 
ciently vigorous to sustain life without their assistance, 
the cotyledons, in most plants wither and die. The num- 
ber of cotyledons varies in different plants, and there are 
some plants which have none. 
Acotyledons, are those plants which have no cotyledons in 
their seeds ; sucji as the cryptogamous plants, mosses, &c. 
Mono-cotyledons, such as have one cotyledon or lobe in the 
seed ; as the grasses, the liliaceous plants, &c. 
Di-cotyledons, seeds with two cotyledons : they include the 
greatest proportion of vegetables ; as the leguminous , the syn- 
genesious, &c. 
Poly-cotyledons. Those plants the seeds of which have more 
than two lobes : the number of these is small; the hemlock and 
the pine are examples. 
The number of cotyledons seldom varies in the same family 
of plants : it has therefore been assumed by some botanists as 
the basis of classification ; but there are difficulties attending a 
method wholly dependant on these organs. In order to be cer- 
tain as to their number, it is necessary to examine the seed in 
a germinating state, which often is difficult. The natural 
method of Jussieu is founded upon the number of cotyle- 
dons. 
The Embryo , is the most important part of the seed, as it 
forms the new plant ; all other parts of the seed seem but sub- 
servient to this. The embryo has been called the Corculum, 
or heart : it is the point from whence the life and organization 
of the future plant originate. In most dicotyledonous seeds, as 
the bean, orange and apple, the embryo may be plainly disco- 
vered. Its internal structure, before it begins to vegetate, is 
very simple, consisting of a uniform substance, enclosed in its 
appropriate bark or skin. When the vital principle is excited 
to action, vessels are formed and parts developed which seemed 
not previously to have existed. The embryo is usually central 
and enclosed by the cotyledons: sometimes it is no more than a 
Cotyledons — Number of cotyledons made the basis of classification — 
Embryo. 
