the flowers as on the bloom of buckwheat. The honey is apparently the same as that of red clover. (Fig. 48.)
Red Clover (Trifolium pratense). The flowers of red clover are almost wholly self-sterile, and, in the absence of cross-pollination, produce very little seed.
As the extensive cultivation of red clover is of primary importance to the agricultural prosperity of this country, its manner of pollination becomes of great practical interest. There has been much discussion in the agricultural and bee journals as to the relative value of bumblebees and the honeybee as pollinators of this species, and a brief review of the available data is desirable as an encouragement to further investigation.
In Europe and America red clover is very largely self-sterile. In England Darwin protected 100 heads of red clover from insects during the blooming period and not a single seed was produced; while a similar number of heads, exposed to insects, produced an average of 27 seeds per head. In the United States, Westgate obtained from 757 heads covered with tarlatan an average of only one-tenth of one per cent, seed per head. Many similar results have been obtained by other experimenters. But Waldron and others have found that a small quantity of seed may be produced by natural self-pollination. As in the case of many other plants, climate may exert an influence on seed production.
In Great Britain and continental Europe, where there is an abundant rainfall and the floral tubes attain their normal length, bumblebees, according to Darwin, Mueller, Knuth, and all other flower ecologists, are the chief pollinators of red clover. Mueller gives a list of ten species of bumblebees taken on the flowers. But he also reports seeing hundreds of honeybees collecting pollen on red-clover bloom, and effecting cross-pollination. Many species of solitary bees also gather the pollen and effect cross-pollination.
Previous to the introduction of bumblebees into Australia and New Zealand red-clover seed could not be produced commercially. (See “History of the Humble-Bee in New Zealand,” by I. Hopkins, Chief Government Apiarist, N. Z. Dept. Agr. 1914. Also “New Zealand’s Experience with the Red Clover and Bumblebees,” by S. Graenicher, Bull. Wis. Nat. Hist. Soc., Vol. VIII, 1910.) Hopkins observed at Metamata that honeybees gathered a considerable amount of pollen from red-clover blossoms. In order to make a thorough test of their value as pollinators of red clover, a number of strong two-story colonies were placed in the center of a 700-acre tract of this plant. The second crop of flowers was just opening. The bees gathered both pollen and nectar; but, when the flowers were later examined for seed, a head here and there contained a good many, others very few, but the great majority of heads contained none. This experiment was made before the importation of bumblebees. After several lots of bumblebees had been brought from England and they had become common, many farmers reported that almost every clover head was full of plump seed, and as high as 720 pounds to the acre were obtaind at Waterlea. A large amount of additional evidence is given in the papers mentioned above. It is also well known that in Australia honeybees were not reliable pollinators of red clover, and profitable crops of seed were not produced until after the introduction of bumblebees. A similar experience is reported from the Philippine Islands.
In the United States, according to the reports of many beekeepers and farmers, honeybees gather a large amount of nectar from red clover, when the floral tubes are shortened by drought, or when the nectar is secreted so copiously that it largely fills the tubes and a portion of it is readily accessible to honeybees. In many localities hundreds of pounds of red-clover honey have been secured. On the fertile limestone soils of the white-clover belt, red clover, like white clover, yields nectar very freely, and is visited by thousands of honeybees. Under these conditions many beekeepers believe that they are important pollinators of the bloom. It is the opinion of E. R. Root, after numerous interviews with county extension agents and farmers,