Self-sterility in Dewberries and Blackberries 
19 
normal plants, when cross-pollinated with self-fertile varieties, very 
frequently set normal berries, while those petaliferous blooms which 
are the direct result of the action of fusarium very seldom if ever set 
fruit. The reason for this can he attributed to the destruction by the 
fungus of the essential organs in the flowers. 
Sometimes, as in the case of the variety Manatee when cross-pollinated 
with pollen from self-sterile varieties, only nubbins are produced; how¬ 
ever, this phenomenon is explained elsewhere in this bulletin, and will 
not be discussed at this point. 
•‘Double Blossom” is not always revealed by the phenomenon of 
petalization. Many flowers that are apparently normal never set any 
fruit. In such cases only the sexual organs have been affected by fusa¬ 
rium, and consequently no fruit was produced. Careful examination of 
the flowers of all of our varieties that are affected with sterility, how¬ 
ever, revealed only a very few traces of the disease. 
The Daily Blooming Period. —In searching for the underlying cause 
of sterility in dewberries, it was deemed advisable to investigate the 
daily blooming period, and the relative time of dehiscence of the anther 
sacks. Blowers of Rubles villosus were observed opening at different 
times, some in the morning hours, some at noon, and still others in the 
afternoon. In fact, flowers in all stages of opening could be observed 
during all times of the day, depending, of course, upon the conditions of 
the weather. 
Blowers of the different varieties of Rubus trivialis were observed to 
behave in a very similar fashion to those of R. villosus; hence the daily 
blooming periods of the two species, in this respect, are quite similar. 
The anthers also were investigated as to the time of their dehiscence. 
It was found that in neither case did all of the anthers dehisce at the 
same time. Anthers sometimes burst before the petals expand, but in 
the majority of cases dehiscence begins after the flower has fully opened. 
The outer cycle of stamens first begins to shed its pollen, and the other 
or inner cycles follow in the order of their maturity. Generally speak¬ 
ing, twelve to twenty four hours elapse before the last anther in the 
flowers has burst. 
Because of this continuous shedding, a scarcity of pollen cannot be 
held responsible for the nonsetting of fruits, because any insect visiting 
such flowers cannot fail to become coated all over with the powdery 
element and transfer the same to other flowers. 
Both species of dewberries were carefully observed in this respect, 
and as no difference in their behavior was found, we were forced to con¬ 
clude that the daily blooming period and the time of the shedding of 
pollen has no effect on the general question of sterility. 
The Amount of Pollen Produced. —By comparing the flowers of the 
self-fertile varieties with those of the self-sterile varieties, we observe 
at a glance that, with a few exceptions, the former produce far more 
pollen than the latter. This fact at once raises the question, Does the 
