COWPEAS 



507 



Insect visitors are numerous, but they are attracted mainly 

 to the extra-floral nectaries at the base of each flower. 

 Natural cross-pollination is usually very rare, but in a few 

 localities, as at the Michigan Experiment Station, occurs 

 abundantly. This is probably due to bumblebees, but 

 exact observations are lacking. . Through such chance 

 crosses the majority of American varieties of cowpeas 

 have probably arisen. 



619. Seed yield. Varieties of cowpeas vary strikingly 

 in their seed production, the bunch varieties usually yield- 

 ing more seed than the trailing sorts. Moreover, the 

 yield of seed with the same variety varies greatly from 

 year to year, depending upon weather conditions and 

 according to locality. In favorable seasons, good produc- 

 ing varieties yield from fifteen to thirty bushels to the 

 acre, while in unfavorable seasons the same varieties may 

 yield only five to ten bushels to the acre. 



TABLE SHOWING ACRE YIELD OF COWPEA SEED AT VARIOUS 

 EXPERIMENT STATIONS 



