RED-CLOVER SEED PRODUCTION. 7 



alas are pressed downward and the stigma and anthers are thrust up 

 against the bee's head. Since the carina and stamens are elastic, the 

 pollen is thrown with considerable force against the head of the bee. 

 When the bee releases the pressure on the carina and alas, the parts 

 return to their normal position on account of the elasticity of the 

 base of the carina and a small dilated vesicular process at the base 

 of each ala. v (Fig. 1.) 



LENGTH OF THE COROLLA TUBE OF RED-CLOVER FLOWERS. 



The corolla tube of red clover is stated by Knuth (22, v. 2, p. 289) 

 and Muller (29, pp. 184-186) to be from 9 to 10 millimeters in length. 

 Pammel and King (32) report an average length of 9.4 millimeters 

 for 450 flowers. Schachinger, according to Fruwirth (12, pp. 163- 

 166), says the corolla tubes are shorter in the second crop than in 

 the first crop, and for this reason smaller bees are able to work on the 

 second crop than on the first. 



Fifteen corolla tubes from each of 28 heads of first-crop red clover 

 were measured at Ames, Iowa. The greatest variation found in 

 different flowers of the same head was 2 millimeters. The 420 

 corolla tubes varied from 8.5 millimeters to 11.5 millimeters, with 

 an average length of 9.6 millimeters. 



DEVELOPMENT OF THE FLOWERS OF RED CLOVER. 



The stamens of red clover develop much more rapidly than the pistil, 

 and the length of the longer set exceeds that of the pistil until near 

 the time the flower opens. The pollen is formed in the longer stamens 

 through the division of the mother cells when the pistil is about 0.25 

 millimeter in length. The division in the pollen mother cells of the 

 shorter stamens closely follows that in the longer stamens. When 

 the pistil is about 1 millimeter in length, only about one-twelfth of 

 its length at maturity (fig. 2, A), the pollen grains are apparently 

 mature so far as their size, their shape, and the thickness of their 

 walls are concerned. At this stage the two ovules are well formed, 

 but the egg and endosperm cells are not developed till later and are 

 not ready for fertilization until just previous to the opening of the 

 corolla. The later development of the pollen consists in protoplasmic 

 changes. After the pollen grains have reached their mature size and 

 their walls have become mature the protoplasm shows very little or 

 no granular nature. Just before the flowers open the protoplasm 

 becomes very dense. At this stage the protoplasm contains much 

 oil hi the form of an emulsion. The pollen will now germinate. 



The pistil has a stylar canal reaching from the ovary almost to 

 the stigma. Just previous to and during the opening of the corolla 

 the pistil elongates more rapidly than the stamens, and as a result 

 the stigma is usually pushed beyond the anthers in the open flower 



