POLYEMBRYONY 



345 



expense of the suspensor. In Nicotiana rustica Cooper (1943) noted 

 an ovule with two embryos of which the smaller had apparently 

 arisen as an outgrowth from the apex of the primary embryo. 

 Kausik and Subramanyam (1946) figure an embryo sac of Isotoma 

 longiflora in which an additional embryo seems to have budded out 

 from a suspensor cell. 10 



It is only in the family Orchidaceae that cleavage polyembryony 

 seems to be of more frequent occurrence. In Eulophia epidendraea, 



Fig. 195. Polyembryony in Eulophia epidendraea; drawings made from whole 

 mounts of ovules. A, zygote has given rise to group of cells, three of which have 

 divided to form independent embryos. B, "bud" arising from right side of embryo. 

 C, two embryos presumed to have arisen by splitting of a single embryo; large 

 vacuolate cells belong to suspensor. (After Swamy, 1948.) 



which may be cited as an example, Swamy (1943) records the 

 following variations: (1) the zygote divides irregularly to form a 

 mass of cells, of which those lying towards the chalazal end grow 

 simultaneously and give rise to multiple embryos (Fig. 195A); (2) 

 the filamentous proembryo becomes branched and each of the 

 branches grows into an embryo (Fig. 195C) ; (3) the proembryo gives 

 out small buds or outgrowths which may themselves function as 

 embryos (Fig. 1955). 



ln It may be noted that some of the above-mentioned examples of cleavage 

 polyembryony may equally well be interpreted as cases of an intimate juxtaposition 

 of two embryos (see Fagerlind, 1944). For some reason, this possibility has not 

 been taken into account by most workers. 



