THE EMBRYO AND THE SEED 



315 



The three primary antipodal cells (ant. Fig. 216, p. 295) have no 

 wall up to the time of fertilisation. Their subsequent behaviour is 

 variable. Sometimes they are at once disorganised ; but in most 

 other cases they remain functional. They may grow to large size, as 

 in many Ranunculaceae ; or they may undergo fragmentation of 

 nuclei, and even cell-division, so as to form a considerable tissue, as 

 in the Compositae and other Gamopetals. Their use appears to be to 

 act as intermediaries between the vascular supply and the enlarging 

 embryo-sac, before the endosperm is organised as a tissue. To that 

 end they sometimes develop as suckers penetrating the chalaza. But 

 in any case they only help towards the final end, which is the full 

 development of the germ. 



The Endosperm. 



The triple fusion, of the two polar nuclei with the second male 

 gamete, has already been noted (Figs. 227, 229). The first division of 







/v « 



c J "' 



Fig. 234. 

 Successive stages of development of the endosperm in Myosvrus. (After Stras- 

 burger.) (i.-ii. and iv.-vii. x 400 ; iii. x 170.) i. shows state at fertilisation. 

 ii., embryo-sac much enlarged, and first division of the fusion-nucleus, iii. shows 

 embryo-sac still more enlarged ; it is on a lower scale of magnification, iv.-vii., 

 stages of cell-formation round the numerous nuclei, derived by division from the 

 fusion-nucleus. 



the resulting triple-fusion-nucleus usually precedes that of the zygote 

 (Fig. 234, i. ii.) : it is repeated synchronously, in rapid succession, so 

 that the numerous nuclei formed are found to be in corresponding 

 stages of division, and their number at any moment is some power of 



