SPERMATOPHYTES : ANGIOSPERMS 
369 
244. The embryo, When the oospore germinates, a more 
or less distinct suspensor is usually formed, but never so 
prominent as in Gymnosperms ; and at the end of the sus- 
pensor the embryo is developed, which, when completed, is 
more or less surrounded by nourishing endosperm, or has 
stored up within itself an abundant food supply. 
The two groups of Angiosperms differ widely in the 
structure of the embryo. In Monocotyledons the axis of 
the embryo develops the root-tip at one end and the " seed- 
leaf" (cotyledon) at the other, the 
stem-tip arising from the side of the 
axis as a lateral member (Fig. 329). 
Naturally there can be but one coty- 
ledon under such circumstances, and 
the group has been named Monocoty- 
ledons. 
In Dicotyledons the axis of the 
embryo develops the root-tip at one 
end and the stem-tip at the other, 
the cotyledons (usually two) appear- 
ing as a pair of opposite lateral mem- 
bers on either side of the stem-tip 
(Fig. 328). As the cotyledons are 
lateral members their number may 
vary. In Gymnosperms, whose em- 
, j, , , . , , P. FIG. 329. Young embryo of 
bryos are of this type, there are often water plantain (Alisma ^ a 
several cotyledons in a cycle (Fig. 
315) ; and in Dicotyledons there may 
be one or three cotyledons ; but as a 
pair of opposite cotyledons is almost 
without exception in the group, it is 
named Dicotyledons. 
The axis of the embryo between the root-tip and the 
cotyledons is called the hypocotyl (Figs. 143, 315, 331), which 
means " under the cotyledon/' a region which shows pecul- 
iar activity in connection with the escape of the embryo 
Monocotyledon, the root 
being organized at one 
end (next the suspensor), 
the single cotyledon ((7) 
at the other, and the stem- 
tip arising from a lateral 
notch (v). After HAN- 
STEIN. 
