438 BOTANY OF CROP PLANTS 



mon in red clover, the larger percentage usually being in 

 the first crop. This is probabjy one of the chief reasons why 

 the second crop of clover is more commonly used for seed. 

 An additional advantage in harvesting the second crop for 

 seed rather than the first is that the farmer is able to get two 

 crops in a season, for if the first crop is allowed to seed, there 

 is insufficient food supply, and in some instances a season too 

 short, for the development of a vigorous second growth. In 

 addition to the reason given above for the 

 relatively light peld of seed in the first crop, 

 it is claimed that pollinating insects are not 

 abundant enough, and that the plant is occu- 

 pied with the production of new shoots rather 

 than reproductive activity. In general, a 

 rank-growing plant is not a good seed producer. 

 Frui° of^^red When the capsule is mature, the stylar end 

 clover (Trifo- separates from the basal part by an irregular 

 mucheniarged! transvcrse line. The upper part of the cap- 

 sule, together with the style, comes off as a 

 lid (Fig. 185), and the single seed escapes. The seeds are 

 kidney-shaped, and yellow, or mixed yellow and violet in 

 color. 



Pollination. — Red clover flowers are protandrous. The 

 work of Westgate and Coe estabUshes the fact that "red 

 clover flowers must be cross-pollinated in order to set seed 

 on a commercial basis." The poUen must come from a 

 separate plant, for even when taken from flowers of the same 

 plant, the percentage of seed set is very small. The bumble- 

 bee (Bombus) is the most important insect visitor of the red 

 clover. It is capable of pollinating 30 to 35 flowers a minute. 

 Honey bees are also efficient pollinators. When the bumble- 

 bee lights on the clover head and inserts its proboscis into 

 the staminal tube, its weight presses down on the keel and 



