SWEET-CLOVER SEED. 15 
of this cage was to determine whether the partial shading of the 
plants in the cages covered with cheesecloth would have any effect 
upon the setting of seed. 
The cage covered with wire netting having 14 meshes to the linear 
inch was used to determine the efficiency as pollinators of sweet 
clover of insects so small that they could pass through openings of 
this size. 
The plants used in the experiments at Arlington were growing 
close to the center of a field of sweet clover. Volunteer plants in a 
field that contained only a scattering stand were used at Ames. The 
cages were placed over the plants in all of these experiments before 
any of the flowers opened, and the work was continued until they 
were through blooming. 
PLANTS SUBJECT TO INSECT VISITATION AT ALL TIMES. 
A plant subject to insect visits at all times and growing in the same 
plat as those inclosed in the cages at Arlington was selected as a 
check to those inclosed in the cages during their entire flowering 
period or for only a portion of it. This plant, which was in bloom at 
the same time as those inclosed in the cages, produced 196 racemes 
with an average of 20.4 pods each. As all of the racemes were col- 
lected and as those on the lower portions of the plant were smaller 
than those on the upper branches, the average number of seeds per 
raceme is much lower than it would have been if only the larger 
racemes had been collected. 
An isolated plant that was subject to insect visits at all times was 
selected for a check to the cage work conducted at Ames. This was 
necessary in order to get results that would be comparable with those 
obtained from the plants inclosed in the cages, as the cage experi- 
ments at Ames were conducted with isolated plants. The plant pro- 
duced 239 racemes, with an average of 41.6 pods. 
PLANTS PROTECTED FROM INSECT VISITATION DURING THEUl ENTIRE FLOWERING 
PERIOD. 
On July 3, 1916, a cage 3 feet square and 3| feet high, covered with 
cheesecloth, was placed over three sweet-clover plants at Arlington. 
(Fig. 6.) This cage was not opened until August 3, when practically 
all of the racemes had passed the flowering stage and the few seeds 
that formed on some of them were practically mature. The three 
plants inclosed in the cage produced 904 racemes, with an average 
of 0.63 pod each. No pods were produced on 594 racemes, while 150 
produced but one each. None of the racemes produced more than 
five pods. 
