430 ReporT OF THE HORTICULTURAL DEPARTMENT OF THE 
blossoms are at a standstill for a time, seeming to have been checked 
in their power to grow by the chill. The evil effects of cold are 
greatly magnified when accompanied by rain. No condition of 
spring-time weather is as harmful to blossoms, except a killing frost, 
as a prolonged cold rain. 
It is quite probable that hot weather also occasionally injures 
fruit blossoms, both by preventing the germination of the pollen, 
by acting directly on the pollen tube or by drying up the secretion 
of the stigma, or by “blasting” the blossom through too rapid 
growth. There is, in all probability, then, a certain range of tem- 
perature necessary for the best fecundation of fruit blossoms, though 
unfortunately there seems to have been no careful field work to 
determine either the maximum or the minimum temperatures for 
the process as it occurs at its best. | 
There seem to be no statements from direct experiments as to 
the comparative effects of high and low temperature on the sexes 
in blossoms but my own observation is that the stamens are more 
sensitive to heat or cold than the pistils. In 1901 while working 
with students in cross-pollination experiments it was found that the 
stamens of several varieties of apples and pears, after a wave 
ef exceptionally hot weather, had developed much more rapidly 
than had the pistils, and that the anthers were bursting with 
pollen, while the stigmas were not yet receptive. The pollen was 
scattered before the stigmas became receptive. Normally, with 
the varieties observed, the stigmas matured with or somewhat be- 
fore the anthers. Such observations as I have been able to make 
in the years since 1901 have convinced me of the correctness of the 
cbservation, for apple and pear fruits at least. Stamens seem to 
develop least rapidly in cold and, as with heat, are seemingly most 
affected by it; though the pistils are more easily injured by frosts. 
After a light frost it will almost invariably be found that many or 
all of the pistils are destroyed or badly injured while the stamens 
may be uninjured or may show but little damage. 
In the current discussions of cross-pollination it is held that in 
some species and their varieties the stamens mature either before or 
after the stigmas become receptive, as the case may be. This is 
supposed to characterize the species or the variety. But it may be 
that the stamens will mature first one season and the pistils first 
another, according as to whether the weather is cool, temperate, or 
warm. This phase is one that deserves close attention from students 
of blossom biology. 
