1912] STEVENS—HETEROSTYLOUS PLANTS 303 
seem to appear so early in their development. The fact that the 
cells are small and vary somewhat in size makes it difficult to 
determine when the difference becomes most pronounced; but it 
will be clear from a comparison of the figures that at diakinesis, 
the heterotypic division, and the formation of the tetrad, some 
difference in size is evident. Compare figs. 50 and 51, 55 and 56, 
and 59 and 60. 
SEPARATION OF THE POLLEN GRAINS 
The daughter nuclei of the homotypic division show at an 
early stage a nucleolus similar in staining reactions to that of inter- 
kinesis (figs. 59 and 60). That is, the nucleoli stain with hema- 
toxylin exactly the same as the chromosomes, so that in early 
stages of nuclear formation it is impossible to distinguish them, 
and the nucleolus appears to arise by a fusion of the chromosomes. 
Staining with safranin, however, shows clearly that the nucleolus 
arises separately, but increases in size as the chromosomes lose their 
staining capacity. 
The separation of the pollen grains takes place in much the 
same way as in the buckwheat, except that in Houstonia the “kino- 
plasmic”’ fibers connecting the nuclei of the tetrad are much more 
clearly marked and persistent. The walls which surround the 
mother cells and separate the cells of the tetrad are not so thick or 
resistant as in the buckwheat. 
Summary of observations 
Fagopyrum esculentum 
The flowers, as a rule, are true to form, but occasional “equal- 
styled’ flowers are found on both long-styled and short-styled 
plants. None of these ‘‘equal-styled” flowers have been proved 
to be fertile. 
In the case of legitimate pollination less than 18 hours is required 
for the growth of the pollen tube and the fusion of the egg and 
sperm nuclei. Illegitimate fertilization is possible, at least in part 
of the cases; but in case of illegitimate pollination more than 72 
