20 
BULLETIN S44, U 
DEPARTMENT OF AGRICULTURE. 
belief, as it is doubtful whether the shading of the flowers on the 
lower racemes is more than that caused by the cheesecloth. It is 
probably the lack of pollination that causes this decrease in seed pro- 
duction on the lower branches of plants growing close together, as a 
vast number of flowers open each day on portions of the plants which 
are exposed directly to visitation by insects and are therefore more 
accessible to them. 
In order to obtain information upon the number of flowers that 
produce seed on the upper and lower portions, respectively, of sweet- 
clover plants when grown under field conditions and where the stand 
contained four to five plants to the square foot, a number of racemes 
were labeled on different portions of the plants at Ames in 1915 and 
1916. When the pods were partly mature, records were made of the 
number of flowers that produced pods. The results obtained are 
given in Table VI. 
Table VI. — Relation of the position oj 
duction. at Ames. 
sweet-clover flowers on the pi 
loo: a., in 1915 and 1916. 
ants to seed pro- 
Position of the flowers. 
Nv.n' e: 
of 
flowers. 
Pods formed. 
Year. 
Number. 
Percent- j , 
age. -^ T era s e. 
1915 
1916 
1915 
Upper half of plants 
do -. 
S12 3-57 
261 101 
344 44 
do 
21o 
The flowers on the upper racemes of the plants produced 31.2 per 
cent more pods than those on the lower racemes in 1915. and 11.4 per 
cent more in 1916. These results prove that insects more frequently 
visit the flowers that are directly exposed and are therefore more 
accessible. 
INFLUENCE OF THE WEATHER AT BLOSSOMING TIME UPON SEED 
PRODUCTION. 
The seed production of sweet clover is seldom satisfactory when 
rainy or muggy weather prevails during the flowering period.- In 
order to obtain data as to the relation existing between the visits of 
insects and the prevailing weather conditions, a record of insect visits 
and of the number of flowers that opened each day was kept for a 
period of nine days at Ames in August, 1915. 
In this experiment the racemes were marked early each morning 
just above the last flowers which had opened the previous day, and 
early the following morning the number of flowers which had opened 
the previous day was noted. The number of flowers that were polli- 
nated was determined by the number of pods that formed. Table 
VII rives in detail the result- obtained. 
