Self-sterility in Dewberries and Blackberries 
31 
normal in all external appearances. To sum it up, tire variety Manatee 
has nothing to recommend it as a fruit producer, and still less as a 
general pollinator for other varieties. 
POLLINATORS FOR THE BERRY PLANTATION 
Although most, of our important varieties of dewberries and black¬ 
berries are self-fertile, the crops might be considerably improved by the 
judicious selection of good pollinators. Pollinators not only serve to 
improve a crop, hut, with many varieties, they are an actual necessity 
for the production of berries. Thus, all of the varieties that spring from 
the species Rubus trivialis need a pollinator in order to set a crop of 
fruit. Other varieties of dewberries are similarly affected, and the 
Fig. 7. —Flower clusters of Snyder and King (blackberries), showing ample pollen production. 
absence, in some cases, of a suitable pollinator practically means the 
total loss of a fruit crop. 
Requirements of a Good Pollinator .—The requirements of a good pol¬ 
linator are the following: first, self-fertility; second, a blooming period 
which is coincident with that of the variety to be pollinated; third, 
the production of an abundance of good viable pollen. 
That self-fertile varieties are most desirable for pollinators becomes 
evident from the fact that during unfavorable weather conditions in 
the blooming season the flowers of such varieties are still able to set an 
abundance of fruit with the aid of their own pollen—they need not wait 
for insects to carry the pollen to them. On the other hand, with varie¬ 
ties not perfectly self-fertile, any condition which affects the activity 
of insects during the blooming season also affects the setting of fruit 
more or less seriously. 
Dewberry and blackberry flowers differ somewhat from flowers in 
