Sr£I;.MAT(jl-llVTES ; ANGKjSrEEMS 



369 



244:. The embryo. — When the oospore germinates, a more 

 or less distinct siispensor is usually formed, but never so 

 prominent as in Gymnosperms ; and at the end of the sxis- 

 fiensor the embryo is developed, which, when completed, is 

 more or less surrou.nded by nourishing endosperm, or has 

 stored up within itself an abundant food supply. 



The two groups of Angiosperms differ widely in tlie 

 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-tij] arising from the side of the 

 axis as a lateral member (Fig. 3"29). 

 Xaturally there can be but one coty- 

 ledon under such circumstances, and 

 the group has been named JLiiKirof//- 

 Jedons. 



In Dicotyledons the axis of the 

 embryo develops the root-tip at one 

 end and the stem-tip at the other, 

 the cotyledons (ustially two) appear- 

 ing as a pair of opposite lateral mem- 

 bers on either side of the stem-tip 

 (Fig. :52s). As the cotyledons are 

 lateral members their number may 

 vary. In (T3'mnosperms, whose em- 

 bryos are of this type, there are often 

 several cotyledons in a cycle (Fig. 

 0I.3) ; and in Dicotyledons there may 

 be one or three cotyledons ; but as a 

 pair of ojiposite cotyledons is almost 

 without exception in the group, it is 

 named DicofiiJedoiis. 



The axis of tlie embryo .between the root-tip and the 

 cotyledons is called the InjpocotiiJ (Figs. 143, 315, 331), which 

 means " under the cotyledon," a region which shows pecul- 

 iar activity in connection with the escape of the embryo 



Fig. .3-^Ei. ViMin^ embryo of 

 water plantain {Alisma). a 

 Monocotyledon, the root 

 being organized at one 

 end (next the suspensorl, 

 the single cotyledon ( C) 

 at the other, and the stem- 

 tip arising from a lateral 

 notch ((■). — After Hax- 

 sTEry. 



