216 



MORPHOLOGY OF ANGIOSPERMS 



of polyembryony, therefore, one of the embryos is to be regard- 

 ed as normal, and the others as secondary or adventitious. Ex- 

 actly the same thing sometimes occurs in Limnocharis emargi- 

 nata, one of the Alismaceae, as observed by Hall S2 (Fig. 101). 



In this species the basal suspensor-cell may 



increase very much in size and remain un- 



divided, as is most common in the Alisma 



type ; or it may divide extensively, forming 



a massive tissue from which several embryos 



bud. It was not observed whether more 



Fig. 102.— Mimosa Den- than one embryo matures, but presumably 



hartu. Tiiree embryos not. This case is interesting not onlv on 



occupying position of aeeoimt of the po lyembryony, but also be- 



egg-apparatus; x 384. • .1 w 1 A i 



—After Gdionabd.« cause it emphasizes the relation between the 



Alisma and Lilium types of embrvogenv. 

 Illustrations of ordinary apogamy are relatively numerous, 

 apparently every cell within the embryo-sac being able under 

 certain conditions to produce an embryo. In some cases a 

 synergid is fertilized, and then the resulting embryo should 

 probably be regarded as normal ; it certainly is not apogamous. 

 For example, Schwere 40 discovered 

 synergid fertilization in Taraxacum 

 officinale ; and Guignard 6S has ob- 

 served that in Xaias major the per- 

 sistent synergid instead of the pri- 

 mary endosperm nucleus may be fer- 

 tilized bv the second male nucleus, 

 resulting in two embryos lying side 

 by side (Fig. 103). An embryo from 

 a synergid in addition to a normal 

 embryo from the egg has been re- 

 ported by several observers. In Mi- 

 mosa Denhartii Guignard 21 has found 

 cases which suggest the development 

 of embryos from all three cells of the 

 egg-apparatus. Sometimes two simi- 

 lar embryos appear, one in the position of the egg and the 

 other in that of a synergid; sometimes a group occurred con- 

 sisting of one unchanged svneraid, one embryo in the egg 

 position, and a second embryo in the position of the second 



Fig. 103. — Xaias major. Two 

 embryos, one from fertilized 

 egg, the other from fertilized 

 synergid, a male nucleus hav- 

 ing fused with nucleus of 

 synergid instead of polar nu- 

 cleus ; e, endosperm nucleus ; 

 x 176. — After Guignard.** 



