268 



I am sending a brief account of about 

 all that is known in regard to the pollina- 

 tion of alfalfa up to the present time. Last 

 summer I cultivated a bed of this valuable 

 fodder plant in my garden for the purpose 

 of studying the relation of the flowers to 

 insects; but, unfortunately, the season was 

 very wet, the leaves rusted badly, and feAv 

 flowers were produced. 



It is well established by numerous obser- 

 vations that honeybees do not usually pol- 

 linate the flowers of alfalfa, but obtain the 

 nectar through a hole in the side of the 

 flower. That is, there is an imperfection 

 in the structure of the flowers which the 

 keen observation of the honeybee quickly 

 discovers. It can extract the nectar more 

 easily through this crevice than in the nor- 

 mal way. So far as beekeepers are con- 

 cerned this is an advantage, since a bee re- 

 quires less time to gather its load of nectar. 



The flowers are often pollinated by bum- 

 blebees, though they, too, sometip::es pilfer 

 the nectar; by butterflies and by leaf-cut- 

 ting and mason bees. The two last-named 

 genera, which are provided with a pollen- 

 brush on the under side of the abdomen, are 

 better adapted for this purpose than the 

 honeybee. There are many species of the 

 leaf-cutting bees {Megaclnle), and in cer- 

 tain localities they are so abundant as to 

 defoliate trees. So far more than 24 specaes 

 of wild bees have been obsen-ed on the 

 flowers, besides many butterflies, flies, and 

 beetles. Just how many are efficient pol- 

 linators is not known. Many are not. In 

 South America the flowers of alfalfa are 

 often visited by small birds resembling 

 hummingbirds, called honey-suckers. 



A single normal visit is sufficient to effect 

 pollination, and all further visits are use- 

 less. The flowers are known as explosive 

 flowers. The anthers and stigma are held 

 in the keel under tension. When a bee 

 presses down the wings and keel it pulls, 

 says Burkill, two triggers and fires oif the 

 flowei' — that is, the anthers and stigma fly 

 forcibly upward and out of the keel, and 

 the pollen is thrown against the body of 

 the bee — a kind of catapult. The stigma is 

 a little in advance of the anthers, and 

 strikes the pollen-brush of the insect first. 

 Both of these organs then move upward 

 against the standard, where they are out 

 of the way and do not again come in con- 

 tact with insects. 



The flower should now cease secreting 

 nectar, since nothing is gained by the at- 

 traction of further visits from insects; but 

 here we meet with another imperfection, 

 for the secretion continues. Insects, there- 

 fore, continue to visit the exploded flowers, 



GLEANINGS IN BEE CULTURE 



when it would be of much gi'eater advan- 

 tage to the plant species for them to visit 

 exclusively flowers not yet pollinated. 



Tlie flowers can not be pollinated by the 

 wind ; and, according to Urban and Burkill, 

 they do not possess the power of self-fertili- 

 zation, even when the stigma is surrounded 

 by pollen. According to the latter observer, 

 the stigma does not become receptive in the 

 absence of insects until it has been rubbed 

 or scratched by a brush or a needle. The 

 reason for this is, I believe, largely mechan- 

 ical rather than physiological. The stigma 

 is covered with papillae, which may some- 

 times prevent the pollen grains coming suf- 

 ficiently near to receive the stimulus neces- 

 sary to excite germination. But when they 

 are rubbed between the papillge by the pol- 

 len-brush on the bee, germination promptly 

 follows. A slight change in the conditions, 

 wliich probably often occurs, as greater 

 sensitiveness on the part of the stigma, or 

 greater pressure, would induce self-pollina- 

 tion. Henslow records that plants he pro- 

 tected yielded more seed than those left un- 

 protected. In cold wet weather the flowers 

 wither without exploding. Where the vines 

 are cut before they bloom, as is the increas- 

 ing 2Jractice in the West, it is, of course, of 

 no consequence whether the flowers are pol- 

 inated or not. When alfalfa is cultivated 

 for its seed, there is, so far as I know, no 

 complaint that the flowers are sterile. 



]\Ir. Stevens says that he saw 584 visits 

 made by " bees " (not by one bee) in about 

 an hour, and that in nine instances the 

 flowers were exploded or " tripped." It is 

 probable that many of these flowers were 

 already exploded. This observation is of 

 considerable interest in showing that the 

 honeybee is of real importance in the pol- 

 lination of alfalfa; and it is to be regretted 

 that he did not give the matter more atten- 

 tion, for Mueller never once saw honeybees 

 visit the flowers legitimately. A man could 

 hardly watch closely for an hour more than 

 five square feet; and if in this area there 

 were nine cases of pollination, then at the 

 same rate there would be about 8000 on an 

 acre of alfalfa, or in ten hours 80,000 flow- 

 ers pollinated. It is to be remembered that 

 only one visit is required, and that subse- 

 quent visits are valueless. Of course, si;ch 

 an estimate based on a single observation is 

 to be taken with great latitude ; but it in- 

 dicates that the honeybee is of more signi- 

 ficance in the pollination of this species 

 than has been commonly supposed. 



Even if the flowers of alfalfa can not 

 fertilize themselves in Europe it does not 

 follow that this is true in western North 

 America. There are well-known instances 



