288 ' BOTANICAL GAZETTE [APRIL 
had not been accidentally pollinated, and were castrated to pre- 
vent self-pollination. They were then pollinated artificially, either 
with pollen from a’plant of the other form “legitimately,” or with 
pollen from another plant of the same form “‘illegitimately.” 
After a definite number of hours, the pistils were fixed and 
microtone sections prepared. In the case of legitimate pollination, 
pistils fixed 18 hours after pollination showed regularly a 3-celled 
pro-embryo, and at least three free nuclear divisions had occurred 
in the endosperm. The embryo was usually in the quadrant stage 
24 hours after legitimate pollination. The time elapsing between 
pollination and fertilization seems to have no relation to the dis- 
tance traveled by the pollen tube, for it did not differ perceptibly 
in the two forms. 
Pistils which had been illegitimately pollinated showed when 
sectioned that in 24 hours the pollen tube had made but a very 
slight growth. After 48 hours there was a greater development of 
the pollen tube; and in 3 days (72 hours) a few pistils showed the 
pollen tube extending nearly to the egg. Some of the pistils which 
were fixed 96 hours after illegitimate pollination showed the embryo 
in the 8- or 16-celled stage. 
Under the conditions of the experiment then, if pollen from either 
form was placed on the stigma of a flower of the other form, the 
growth of the pollen tube and the fusion of the two nuclei required 
considerably less than 18 hours. But if pollen from either form 
was placed on the stigma of a flower of the same form, even though 
on a different plant, a period longer than 3 days was required for 
the tube to reach the egg. Illegitimate fertilization would then 
practically never occur in nature, especially in a form so frequently 
visited by insects. H. MULuer records (28, p. 165) 41 species of 
insects seen on the flowers of the buckwheat, many of them very 
frequently. 
It is entirely possible that the rate of growth of the pollen tube 
was more rapid under the conditions of the experiment than it is 
in nature, for the temperature of the greenhouse in which the plants 
were grown was rather high. It does not seem probable, however, 
that this would affect the relative rate of growth of the pollen tube 
in the two cases. 
