McAllister—Cytology and Embryology. 619 
phases of the first division both point conclusively to the hetero¬ 
typic nature of this division. The number of the chromosomes 
was not accurately determined at this stage but it was unques¬ 
tionably much smaller than the somatic number. 
A cell plate is formed in the telophases of the first division 
which splits to form plasma membranes between which a rather 
thick, apparently gelatinous wall is deposited. Even in the 
metaphases the spindle is seen to be nearest the chalazal end of 
the mother cell and during cell plate formation the outer cell 
grows rapidly while the inner one grows very slowly, in 
some cases evidently not at all, so by the time the daughter 
nuclei are ready for the second division the outer cell is several 
times larger than the inner. Although considerable difference 
exists between the daughter nuclei it is not as striking as the 
difference in size between the two daughter cells. 
The second or homoeotypic division occurs immediately after 
the formation of the daughter nuclei and cells of the first di¬ 
vision. Usually the nucleus of the larger outer cell divides 
slightly in advance of the nucleus of the smaller inner cell (Fig. 
37). It is possible that at times the inner daughter nucleus 
does not divide although I could find no positive evidence on 
that point. In the telophases of this division a definite cell 
plate is formed which splits and thus causes the complete sep¬ 
aration of the four macrospores though no cellulose Wall is 
formed (Fig. 38). These four macrospores are not uniform 
in size as are the four macrospores of S. stellata, the two outer 
cells being large and plump while the two inner ones are small 
and often distorted. Nevertheless the evidence is perfectly 
clear that for a time four, perfectly distinct cells exist. The 
lack of cell walls separating all four macrospores does not in 
the least affect their individuality as cells. 
The plasma membranes which are formed by the homoeo¬ 
typic central spindle figures do not form any cell wall as far as 
I have been able to observe and they very shortly disappear 
(Figs. 39 and 40). The plasma membrane and wall formed 
by the central spindle of the first division figure persists and 
we therefore get at this stage, two binucleated cells which have 
