SWEET-CLOVER SEED. 
19 
Table V. — Summary of the insect pollination studies conducted at Arlington, Va., and 
Ames, Iowa, in 1916. 
Num- 
ber of 
plants. 
Method of treatment. 
Number of— 
Location. 
Racemes. 
Pods 
pro- 
duced. 
Pods per 
raceme, 
average. 
1 
1 
3 
12 
3 
1 
1 
2 
1 
Check— subject to insect visitation at 
all times. 
.do , 
196 
239 
904 
2,370 
723 
227 
486 
544 
418 
4, 013 20. 47 
9,943 
577 
653 
2,720 
152 
8,024 
11,397 
17, 186 
502 
41.60 
Protected from all insects 
.63 
.do 
.27 
Visited by night-flying insects only 
(cage 1). 
Visited by night-flying insects only 
(cage 2). 
Visited by night-flying insects only 
Visited by day-flying insects only 
do 
3.76 
Dc 
.67 
16.51 
20.95 
41.11 
Do... 
9 
1,594 
.31 
The results in Table V show that an average of 0.37 pod to the 
raceme was obtained from the plants protected from visitation by all 
insects during the flowering period. As the racemes of Melilotus 
alba will average approximately 50 flowers each, less than 1 per cent 
of them set seed without being pollinated by insects. The results 
obtained in the cages in which only night-flying insects had access to 
the flowers show that these insects pollinate sweet clover to a slight 
extent, but that the number of pods produced by them is so few that 
it may be assumed that these flowers would have been pollinated by 
day-flying insects. This assumption is borne out by the results 
obtained in the cages where only day-flying insects had access to the 
flowers, as the results obtained in these cages at Arlington and Ames, 
respectively, are approximately the same as those obtained on the 
plants subject to insect visitation at all times. It will be noted that 
the yield of seed on the plants visited by insects at Ames is much 
higher than that of the plants subjected to insect visits during the 
same period at Arlington. This difference in seed yield may be 
attributed to the fact that isolated plants were used in the experi- 
ments at Ames, and at Arlington the experiments were conducted 
with plants growing under field conditions. 
RELATION OF THE POSITION OF THE FLOWERS ON MELILOTUS ALBA 
PLANTS TO SEED PRODUCTION. 
Observations of sweet-clover plants grown under cultivation, and 
especially when the stands were thick, showed that the flowers of the 
racemes on the upper and exposed branches produced a larger per- 
centage of seed than those on the lower branches which were less 
exposed. It is thought by some that the failure of the flowers on the 
lower racemes to be fertilized is due to shading; but the results ob- 
tained in the cheesecloth and glass covered cages do not warrant this 
