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Sweetclover 
Pieters, A. J., and Hollowell, E. A. 
1S37. Clover improvement. U. S. Dept. Agr. Yearbook 1937: 1190-1214. 
p. 1207: Pollination of sweetclover under natural conditions 
is effected princip a lly b y honeybe es, except insofar as the species, 
varieties, or individuals are spontaneously self-fertilized. 
United States Department of Agriculture. 
1342. A much larger harvest of hay crop seeds needed in 1942. U. S. 
Dept. Agr. Food for Freedom Program, Background Information 
Series, No. 7, 5 pp. 
p. 3: ... lack of sufficient pollination lowers seed yields. 
Honeybees are the most va l uable poll i nators . A minimum of one hive of 
honeybees per acre located close to a blossoming field of sweet clover 
will increase the quantity of seed set. 
Trefoil 
McKee, R., and Schoth, H. A. 
1941. Birdsfoot trefoil and big trefoil. U. S. Dept. Agr. Cir. 625, 
13 pp. 
p. 5: The general conclusion of investigators who have studied 
seed setting in Lotus species is that both birdsfoot trefoil and big 
trefoil are practically sslf-sterile. Silow ... who has more recently 
given the subject consideration draws the following conclusion: 
" Lotus cornicuiatus is practically self-sterile, but occa- 
sional plants set a few seeds after self-pollination. Plants of 
L.jaa.i or Smith (^ L^ uliginosus Schk.) are, on the whole, incapable 
of spontaneous self-pollination, but after artificial self-pollina- 
tion practically all plants are self- fertile, some to a very high 
degree . Thus these two perennial species are almost entirely de - 
pendent upon insect visitors for seed formation . " 
