ee ee nee 
ihe hn a Bi DA 
a Te eee ee eee eee a) tee 
1900] DEVELOPMENT OF THE EMBRYO-SAC 47 
F1G. 23. The embryo in the two-celled stage; below are three endosperm 
nuclei and the antipodal cells ; this is an abnormal case in which the cross- 
wall was formed up near the center of the embryo-sac. 
Fig. 24. A complete embryo-sac containing a young embryo in which the 
first oblique wall is in the third instead of the fourth cell. 
Fig. 25. A young embryo showing the first oblique wall in the fourth cell 
as is normally the case. 
Fig. 26. embryo at a later stage; the basal cell has become much 
enlarged ; the ee cell forms the remainder of the suspensor, four cells 
only are here shown; the heavy line through the embryo separates the apical 
from the subapical cell, and in the former the oblique wall can also be dis- 
tinguished ; the other divisions are irregular. 
Fic. 27. The oldest embryo obtained ; the basal cell and the derivatives 
of the subbasal cell still persist ; the cotyledon and plumule are differentiated 
as is also the central cylinder. 
Figures 28-35. Canna Indica L. 
Fig. 28. A vertical section through the nucellus showing the hypodermal 
cell slightly larger than those of the surrounding tissue. 
Fig. 29. Same at a later stage ; the hypodermal cell has given rise to the 
archesporial cell and to a primary wall-cell which in turn has divided into 
three or four daughter cells; the archesporial cell is already much enlarged 
and the nucleus is in the spirem stage 
Fic. 30. The first or heterotypic division of the same nucleus in meta- 
phase ; six segments in each group may be counted. 
Fig. 31. The second division of the archesporial nucleus in the nuclear- 
plate stage; three chromosomes only are here present; the cross-wall was 
formed during the previous division. 
IG. 32. The axial row of four cells; the central cross-wall was formed at 
the heterotypic division, the upper and lower at the second division. 
- 33. The axial row with the three upper cells in the process of dis- 
integration ; the lower is growing to become the embryo-sac. 
Fig. 34. The embryo-sac showing two synergids and the egg nucleus at 
the upper end, and three antipodals with the polar nucleus at the base ; the 
upper polar nucleus has traveled part Rt down the lateral wall. 
Fic. 35. Same at a later stage; egg-apparatus is inclosed by a deli- 
cate membrane as are also the ik A antipodals ; the two polar nuclei 
have fused to form the definitive nucleus. 
