RED-CLOVER SEED PRODUCTION. 5 



presence or absence of insects influence seed production. The work 

 of Sirrine (37, p. 89-90), as well as that of Witte (46), showed red clover 

 to be self-sterile. In the experiments of Cook (5), Shamel (36), and 

 Kirchner (21) no seed was produced when heads were covered before 

 blooming and not pollinated. Fruwirth (11; 12, p. 163-166) did not 

 obtain a single seed when heads under cover were left undisturbed 

 or when they were pollinated with pollen from another head on the 

 same plant, while heads pollinated with pollen from another plant 

 produced seed. Bolley (4) obtained but two seeds from one head 

 of a large area which was placed under a fine screen before any of the 

 flowers came into bloom. He states that insects other than bumble- 

 bees must pollinate the flowers, since the bumblebees were scarce 

 and the clover set well. Genevier (13) states that the fertilization 

 of clover does not depend on the presence of bumblebees. Pammel 

 and King (32) report but two seeds from 643 heads which were 

 allowed to mature under a screen cover, while Washburn (45) says 

 that only by the aid of bumblebees was he able to obtain seed. 



Armstrong (1), in writing about New Zealand, says there is every 

 reason to believe that numerous individuals belonging to Trifolium 

 pratense are self-fertile and that they produce self-fertile progeny. 

 According to him the American strain is usually, if not always, self- 

 fertile. McAlpine (24) discusses Garton's experiments, which show 

 that the self-fertilizing property is as common with red clover as it is 

 with the bean. The following is quoted from Kerner (20, p. 407) : 

 "Pisum and Ervum, Lotus and Melilotus, the various species of Tri- 

 folium, almost all of them, when unvisited by insects, ripen seed, 

 only a few species here and there being infertile when dependent 

 upon their own resources." Nothing definite can be taken from 

 Kerner's statement, since he does not quote any species or give defi- 

 nite exceptions to his statement. Hopkins (14) says he is not ready 

 to admit that self-fertilization does not take place and that he is 

 inclined to believe a crop of seed can be grown without the aid of 

 bumblebees. The same author (15, p. 73) states that honeybees 

 serve the same purpose as bumblebees in cross-fertilizing red clover. 

 The work of Beal (2, p. 325-328) shows that bumblebees increased 

 the seed production about four times, since in a check cage he received 

 25 seeds from 50 heads, while in the cage where bumblebees were 

 placed 94 seeds from 50 heads were obtained. Martinet (27) found 

 red clover to be self-fertile, stating that cross-pollination might 

 have been brought about by very small insects (undoubtedly mean- 

 ing thrips). Fruwirth (12, p. 163-166), however, showed that 

 thrips transferred from other clover fields in large numbers produced 

 no seed in his experiments. Meehan (28) states that a careful exami- 

 nation of the clover flower in all its stages convinced him that from 

 its structure and behavior it was self-fertile. It is still an open 



