1906 ENTOMOLOGICAL SOCIETY. 43 



eggs on the crop. In accordance with this, it is now recommended to pas- 

 ture closely until the month of June, when the clover may be allowed to 

 grow for a late crop of seed; or if the crop has been left for hay, to cut this 

 not later than June 20th, and obtain the seed from a second crop. Where 

 these rules are observed, the injuries of the midge can be largely avoided. 

 However, so long as some growers persist in disregarding them, it will find 

 ample means of propagation ; and so long the rest must expect to be obliged 

 to maintain their precautions. 



Having seen how the presence of one insect is so inimical to success in 

 clover seed production, we will notice next how the presence of another is 

 essential to the same. 



Red clover, particularly the first crop, often fails to produce seed freely 

 owing to imperfect fertilization. To understand this we need to notice two 

 facts: 1. This plant is incapable of self-fertilization, and is therefore de- 

 pendent on outside agencies for the performance of this office; and 2. The 

 flower is so constructed, that very few of the agencies which operate in the 

 cross-pollination of other flowers can take part in this case. 



1. Inability to self -fertilize. 



Many plants are known which, owing either to the structure of their 

 flowers, or the ineffectiveness of the pollen on the pistils of the flower from 

 which it is derived, do not self-fertilize. The red clover is an example as 

 we shall notice presently. The flowers or florets of which the head is com- 

 posed, have the four sets of organs which we find in other complete flowers. 

 The corolla is a long tube having its lobes curiously fashioned so as nearly 

 to close the opening or mouth. Within and enclosed in the lower lobes 

 called the keel, are the pistil and surrounding it the monadelphous stamens. 

 Notice particularly that the stigma of the pistil reaches up bevonrl the 

 anthers of the stamens. Owing to this peculiarity, the pollen in falling 

 does not usually come in contact with the stigma, and the plant evidently 

 requires the intervention of insects for its pollination. That this is the case 

 has been repeatedlv provpd bv thp 'exclusion of insects from the clover plants, 

 with the result that under such circumstances no seed was produced. 



2. Limited number of agencies which can pollinate red clover. Since 

 insects do so much in carrying pollen between other plants, let us sef^ why 

 they are not equally useful here. We notice by examining a floret, that in 

 order that pollen from another flower may come in contact with its stigma, 

 it must be borne by some insect which in lighting on the keel, is heavy 

 enough to pull it down so as to release the essential organs (pistil and sta- 

 mens) from it ; and then in probing with its proboscis for the nectar at the 

 base of the corolla, will brush on to the stigma any pollen which may have 

 become attached to it in visiting other flowers previouslv. The nectar, or 

 sometimes the pollen which it bears, is the incentive which brings insects 

 to a flower; but in the case of the red clover, the neck of the corolla tube 

 is so long, that of the insects heavy enough to open the flower, onlv a very 

 few have mouth parts long enough to reach the bottom. Bumble bees 

 (Bomlnis) of various species, are practically the only insects which so habi- 

 tually visit the flowers of red and mammoth clovers, as to be entitled to 

 notice as a factor in their pollination. It is claimed that wasps often visit 

 the flowers for honey, but instead of entering at the mouth in the orthodox 

 manner, thev cut a hole in the sifle within reach of the honey. Bumble 

 bees have also been charged with this to some extent, and honey-bees will 

 follow and utilize the holes thus made, but do not enter the flower; and so 

 do not effect pollination. However, there is no doubt that bumble bees 

 ordinarily visit the flower in such a way as to bring pollen to the stigma. 



