OTHER CLOVERS 415 



strains were grown two years and gave comparative yields 

 as follows: Danish, 100; Ladino, 94; Holland, 92; 

 American, 89; Pomeranian, 86; English, 80; Silesian, 

 76; German, 73. 



In England a number of experiments have shown that 

 if seed gathered from wild white clover plants be sown, 

 the plants will persist much longer than if seed of the cul- 

 tivated plants be sown. The cultivated white clover 

 disappears in one or two years, while the wild white 

 clover persists much longer at least three to five years. 

 The explanation given is that the cultivated white clover 

 is less resistant to the rigorous springs and perhaps also 

 to " clover sickness." 



Werner gives the hay yields to an acre in Germany as 

 ranging from 1760 to 2640 pounds. 



The only American hay yield reported seems to be the 

 following: Pennsylvania Experiment Station, 4133 

 pounds to an acre. 



495. Pollination. White clover has long been valued 

 as a honey plant. If the visits of insects are prevented, 

 only about one-tenth as much seed is produced, according 

 to Darwin's experiments in England. 



Beal in Michigan secured only 5 seeds from covered 

 heads, while 8 uncovered heads contained 236 seeds. 



In an experiment by Cook, 10 heads covered to exclude 

 insects set no seeds, while 10 heads in the open produced 

 541 seeds. 



496. Seed-production. Commercial seed of white clo- 

 ver is grown mainly in Europe (Bohemia, Poland, Russia, 

 Germany, Holland, England), but some is produced in 

 New Zealand. In America seed is produced in Ontario, 

 Michigan, Wisconsin and western Washington. Ladino 

 white clover seed comes wholly from Italy. 



