20 BULLETIN 289, U. S. DEPARTMENT OF AGRICULTURE. 
clover was in bloom very few nectar-producing plants were to be 
found. Whether the honeybee would work on red clover to this 
extent in a year of normal rainfall when the number of other nectar- 
producing plants is larger is problematical, but our observations 
and results show that the honeybee is able to spring the keels of red- 
clover flowers and thereby cross-pollinate them. 
MECHANICAL CROSS-POLLINATORS OF RED CLOVER. 
A machine so constructed that a platform of brushes could be made 
to strike clover heads with a vertical stroke was placed on the market 
under the name of a clover cross-pollinizing machine (fig. 7). This 
machine received some favorable comment. In view of this fact, 
a number of experiments were outlined to test its efficiency and also 
Fic. 7.—Clover cross-pollinizi ig machine. 
to test the efficiency of different types of hand-operated brushes as 
mechanical cross-pollinators of red clover. Some plats of red clover 
were treated with various types of brushes at different times of day, 
while other plats were treated when the clover heads were in different 
stages of bloom. The direction of the strokes with the brushes was 
also varied in order to see whether this would have any effect on 
the yield of seed. 
MACHINE POLLINATION EXPERIMENTS. 
In order to determine the efficiency of a clover cross-pollenizing 
machine several experiments were performed at Ames in 1911. 
Machines similar to the one used were offered for sale on the market 
at the time these experiments were being conducted. 
