SWEET-CLOVER SEED. 
13 
was the open check, 4.3 per cent more flowers set seed than on the 
racemes where the same toothpick was used to spring all the keels, 
but 11.57 per cent more seed was obtained than in experiment C. 
Spontaneous self-pollination occurs to only a very small extent, as 
will be seen from the results of experiment A, in which an average of 
only 2.9 per cent of the flowers set seed. 
Table III. — Effect of different types of artificial manipulation on the seed production 
of sweet clover at Arlington, Va., and at Ames, Iowa, in 1916. 
Location. 
Experi- 
ment. 
Arlington 
Ames 
Arlington 
Ames 
Arlington 
Ames 
Arlington 
Ames 
Arlington 
Ames 
Arlington 
Total number of- 
Racemes. Flowers. Pods set 
ion 
50 
30 
3,510 
4,536 
5,599 
1,276 
1,229 
289 
575 
377 
175 
144 
92 
3,973 
600 
701 
133 
936 
342 
307 
80 
Flowers that set 
seed (per cent). 
At each 
station. 
4.1 
2.0 
70.95 
47.02 
57.03 
46.02 
63.24 
59.47 
81.43 
45.71 
Average. 
2.9 
66.51 
54.94 
62.18 
70.10 
SEED PRODUCTION OF MELILOTUS ALBA UNDER ORDINARY FIELD 
CONDITIONS. 
The production of seed of Melilotus alba under ordinary field con- 
ditions varies considerably, not only in different parts of the country 
but also on different fields in the same region. A number of factors 
contribute to this variation, one of the most important of which 
appears to be the inability of the plant to supply all the developing 
seed with sufficient moisture, causing some of them to abort. As 
pointed out on page 22 this condition was very marked in certain 
parts of the country in 1916. However, poor seed production is 
not always correlated with lack of moisture, for the seed crop was a 
failure in 1915, where cloudy and rainy weather prevailed much of 
the time the plants were in bloom. It is believed that the lack of 
pollination by insects was the principal cause for the failure of seed to 
set, as very few insects visit sweet-clover flowers when such condi- 
tions prevail. As sweet-clover pollen will germinate in pure water 
and as plants which have their roots submerged in water set seed 
abundantly when pollinated, the failure of the seed crop in 1915 was 
not due to excessive moisture. 
As a rule, thin stands of sweet clover produce more seed to the 
acre than thick stands and isolated plants more seed than those 
growing in either a thick or thin stand. The correlation of seed 
