In the monocotyledons the cotyledon has a
cylindrical shape sheathing the stem and its
bud, and developing at the side adjoining the
endosperm, of which we shall speak presently,
into a shield-like structure as in Maize, or
into a globular body as in the Cocoanut.
/Here, as well as in many dicotyledonous
plants, the cotyledons have the function of
absorbing a food-substance, which forms a
separate tissue within the seed coats, and
that is the endosperm. (See germination of Castor seed, of Rice,
and of Cocoanut.) Seeds containing endosperm are termed


Fig. 260.— Endosperm
in the seed of Maize.
ey vit
Yi) ihn TILA \
iy | ‘ft ! Hy ; ‘eh
fh. vi ‘I ati up
bey, hy gee | |
{1
My ra
| Wut


Fig. 261.— Castor seed.
endospermous, and those in which endosperm is not present,
exendospermous. Exendospermous seeds have the food-substance


270 STRUCTURE AND VITAL PROCESSES OF PLANTS


necessary for the growing seedling packed in their cotyledons,
which thus become swollen. The food-substance either contained
by the cotyledons or by the endosperm is also utilized for food
by man, as well as by many animals.
