In germination the cotyledons come above ground and form the first green leaves of the plant.
The embryo consists of an axis bearing two or more cotyledons and ending below in a radicle; it lies in a generally copious food-storing tissue (endosperm) which is the remains of the female prothallus.
In other cases this growing-point becomes active at once, there being little or no elongation of the hypocotyl and tbe cotyledon or cotyledons remaining in the seed.
In cases where the development of the embryo is advanced at the resting period, traces run from the cotyledons and determine the symmetry of the stele of the primitive axis, the upperpart of which often shows stem-structure, in some respects at least, and is called the hypocoty- ledonary stem or hypocotyl, while the lower part is the primary root .~-,
Toffs is largely developed, and the placenta, so far as known, is nondeciduate, the chorionic villi being either evenly diffused or collected in groups or cotyledons (in Pecora).