4 
: 
1899] STRUCTURE OF THE EMBRYO-SAC 157 
alone be distinguished at the upper end of the embryo-sac. 
There is little change in the embryo for some time, and it 
remains undivided until after there is a considerable develop- 
ment of the antipodal cells and endosperm. 
An examination of the antipodal region of the recently fer- 
tilized embryo-sac (fig. 7) reveals a remarkable change in the 
antipodal cells, which seem to be immediately affected by the 
act of fertilization. While the embryo-sac itself has not increased 
appreciably in size, the antipodal cells have now enlarged to 
several times their original dimensions and present all the 
appearances of actively growing cells. The nuclei have divided, 
ane in the specimen figured there were already present eight 
antipodal nuclei. It was difficult to decide whether in all cases 
the division of the nucleus was accompanied by the formation of 
> division wall, or whether, as in some other cases of multiplica- 
Hon of the antipodal nuclei, the division of the nucleus occurs 
without the formation of a cell wall. 
niage first division of the endosperm-nucleus takes place at 
antipod : Same time that the first nuclear-division occurs in the 
ae % Hea The secondary endosperm-nuclei arrange them- 
the wall a way, in the thin layer of protoplasm lining 
size. be = embryo-sac, which now rapidly increases in 
antipodal ea cell-division takes place in the endosperm, the 
divided oan have increased enormously in size, and have 
Projecting int £6 form a conspicuous hemispherical cell-mass 
number js ca the large lumen of the embryo-sac (fig. 8). The 
Stages a re great, more than a hundred, or in some older 
those of an a and fifty, thus exceeding, so far as I know, 
defined Sa =i plants yet investigated. Each cell is clearly 
granular, Th P einty uninucleate. The cytoplasm is very finely 
Certain BA , ie peal: at this stage recall strongly those of 
With a ees. It is very clear that we have to do here, not — 
of Dhysiolog; ary structure, but with one which is undoubtedly 
8ical importance. The endosperm at this stage 1s 
‘Wester 
Lass, “ah rag Zur Embryologie der Phanerogamen, etc. Nova Acta d. kaiserl. 
* Akad. der Naturf. 57: 1-30. 1890. 
