RED-CLOVER SEED PRODUCTION. 5 



OUTLINE OF POLLINATING EXPERIMENTS. 



It is a well-known fact that the yield of clover seed varies greatly 

 from year to year, and no distinct correlation with any marked 

 climatic factors has been determined. It was thought that 

 possibly the absence of suitable pollinating insects, such as bumble- 

 bees, might in some seasons be responsible "for the reduced yields 

 of seeds. This is especially true when conditions were such that 

 there was no other apparent reason for the failure of the crop to 

 set seed. In order to obtain light on this point, a series of experi- 

 ments was outlined to determine (1) whether clover flowers were 

 able to set seed without the assistance of outside agencies; (2) 

 whether clover flowers were able to set seed when their own pollen 

 was transferred to their stigmas by outside agencies; and (3) the 

 relative efficiency of the honeybee and the bumblebee as cross- 

 pollinators of red clover. 



In order to overcome any local environmental factors, the experi- 

 ments were conducted at Ames, Iowa, and La Fayette, Ind., and were 

 repeated to some extent at the Arlington Experiment Farm, Va. 

 The work on individual clover heads was performed on heads pro- 

 tected from the action of insects by tarlatan cloth. This cloth has 

 about twice as many meshes to the linear inch as ordinary mosquito 

 netting. Where numerous plants were to be protected from all 

 outside agencies, cages of wire screen having 14 meshes to the 

 linear inch were used. In some instances, where it was desired to 

 permit the entrance of all insects smaller than bumblebees, cages 

 made of galvanized-wire screen having four meshes to the linear inch 

 were employed. 



All work was done on second-crop red clover unless otherwise spe- 

 cifically stated. 



STRUCTURE OF THE RED-CLOVER FLOWER. 



The heads of red clover contain from 35 to 150 flowers each, and 

 according to Pammel and Clark (30) the average number per head 

 for black loam soil at Ames, Iowa, is 71.1 for the first crop and 98.1 

 for the second crop 



The flowers of red clover consist of a green pubescent calyx with 

 five pointed lobes and an irregular magenta or purple corolla of five 

 petals (Fig 1 .) The claws of the petals are more or less united to 

 the staminal tube This staminal tube is formed by the union of the 

 filaments of the nine inferior stamens To the greater portion of the 

 anterior end of this common tube, formed by the uniting of the claws 

 of the petals with the staminal tube, is attached the broad base of 

 the vexillum. The carina, which is composed of two petals united 

 at one edge, is attached to the inferior part of the edge of the tube 



