1900] DEVELOPMENT OF THE EMBRYO-SAC 45 
At the time of fertilization the two sperm nuclei lie together 
near the egg nucleus, but only one is really in contact with the 
latter. 
The fertilized egg-cell undergoes at first three divisions, form- 
ing a row of four cells. The terminal cell and the one next below 
give rise to the greater part of the embryo. In the subbasal 
cell only one transverse and two vertical divisions ever occur, 
and the cells thus formed together with the very much enlarged 
basal cell form the suspensor. 
Canna.—The heterotypic division is also the first division of 
the archesporial nucleus, and is followed by a transverse wall. 
The second divisions occur simultaneously and are also fol- 
lowed by cell walls. These form an axial row of four cells. 
The lower cell alone gives rise to the embryo-sac; the other 
three finally disintegrate and disappear. The further develop- 
ment is quite normal. 
The nuclei of Canna are more nearly like those of Convallaria 
than Potamogeton. They have a true nucleolus and no central 
chromatin mass. 
The number of chromosomes in the vegetative divisions is six. 
When passing to the poles at the heterotypic division there were 
still six; but later the second division showed only three as the 
reduced number. Probably the segmentations for both divisions 
occur during the prophase of the heterotypic division. This 
number is one of the smallest yet found in vegetable tissue. 
CORNELL UNIVERSITY. 
EXPLANATION OF PLATES VI AND VII. 
Figures 1-11. Convallaria majalis L. 
Fig. 1. A vertical section through a young ovule, showing the epidermis, 
archesporial cell, and two of the wall-cells between ; the archesporial nucleus 
is in the resting stage. 
Fic. 2. The same at a later stage ; the wall-cells have undergone further 
oe and the archesporial nucleus is in synapsis. 
G. 3. The archesporial nucleus in the spirem stage; the ribbon contains 
doait denser portions of chromatin. 
