214 



MORPHOLOGY OF AXGIOSPERMS 



Fio. 99.— FunHa ovata, showing adventitious embryos ; fer- 

 tilized egg has given rise to weak proembryo of three 

 cells: x 190. — After Strasbibgeb." 



the adventitious embryos begin to develop but never mature. In 

 Citrus the embryos are derived not only from the cells of the 



nucellus capping 

 the sac, but also 

 from those lower 

 down, which may 

 be separated from 

 the sac by several 

 cells. In Coele- 

 bogyne, long sup- 

 posed to be par- 

 thenogenetic, fer- 

 tilization never 

 occurs in Europe, 

 since only pistil- 

 late plants are 

 cultivated. These 

 are not cases of apogamy, as often stated, but are evidently 

 cases of vegetative multiplication or budding, since the em- 

 bryos arise from sporophytic tissue. In Opuntia vulgaris 

 (Ganong 49 ) the ripe seed contains one large embryo and sev- 

 eral smaller ones pressed to one side. Half ripe seeds generally 

 show that the large embryo comes from the micropylar end of 

 the sac, while the small ones arise from nucellar tissue. Among 

 Cactaceae the only previously 

 known case of polyembryony is 

 that of Opuntia tortispina. 



The multiplication of em- 

 bryos by budding from a mass- 

 ive suspensor also occurs, and 

 is especially common in the 

 Lihiim ty]ie of embryogeny, in 

 which the suspensor is strongly 

 meristematic. In 1895 Jef- 

 frey"" called attention to the 



fact thai in h'ri/lli muni in mihTl- 



ccuium the suspensor is a mass- 

 ive and lobed tissue on whose 

 free surface two to four embryos appear, onlv one persisting 

 (Fig. loo). As in Finilia, the cells of the nucelhis are 



ft&ft 



Fin. 100. — Erythronium aiyiericannm. 

 Four embryos derived from fertilized 

 egg ; x 144.— After Jeffrey. st 



