THE EMBRYO 21 Y 



synergid ; and in one case three embryos were seen occupying 

 the position of the egg-apparatus (Fig. 102). Although favor- 

 ing this interpretation, Guignard mentions the possibility that 

 the extra embryos may have come from the separation of early 

 -i gments of the egg. a view doubtless suggested by the separa- 

 tion of the cells of the suspeusor in certain of the Legu- 

 minosae. 



In Vincetoxicum nigrum and V. medium ( hauveaud 33 

 finds that polyembryony is a regular phenomenon, one, two, 

 three, four, and even five embryos appearing, more than one 

 of which may reach maturity. The svnergids are doubtless 

 involved. Chauveaud found four or five bodies in the pollen- 

 tube which lie thought might be interpreted as male nuclei, and 

 responsible for polyembryony. He also concludes that poly- 

 embryony is a primitive feature of Angiosperms, the number 

 having been reduced in the interest of one strong embryo. In 

 describing synergid fertilization in Iris sibirica, Dodel 31 im- 

 plies a somewhat similar view, when he interprets the synergids 

 as partially aborted eggs. In this form more than one pollen- 

 tube may enter the micropyle. 



In certain orchids, as Gymnadenia conopsea (Stras- 

 burger 16 ), two embryos sometime occur in the same sac, but 

 their origin is uncertain, although it is very probable that one 

 of them is derived from a synergid, either apogamously or by 

 fertilization. 



In a preliminary paper, Hegelmaier 79 states that polyem- 

 bryony is habitual in Euphorbia dulcis, two to nine embryos 

 appearing at the micropylar end of the sac. One of the em- 

 bryos, which certainly comes from the egg and mav be dis- 

 tinguished from the others by the presence of a suspensor, 

 becomes the functional embryo. Fertilization was not studied, 

 and so the origin of some of the embryos is in doubt, although 

 it is certain that some come from the nucellus. Two embrvos 



t/ 



often reach the cotyledon stage, with tissue systems differen- 

 tiated, while the others appear as irregular masses. 



Allium odorum presents a remarkable case of polyembryony. 

 In 1895 Tretjakow 3fl reported one to three embrvos from the 

 antipodal cells (Fig. 104), the fertilized e^ix and sometimes a 

 synergid forming additional embryos. In the same species 

 Hegelmaier 45 observed five embryos in a single embryo-sac ; 



