80 SOURCES OF NECTAR 
Among the important pollen plants may be mentioned several 
of the forest trees, including the willows, elms and maples already 
mentioned. In addition the box elder, walnut, hickory, ash, 
beech, birch, chestnut and aspens may be mentioned. 
Fig. 45.—Where sufficiently abundant, the wild cucumber is valuable. 
Corn is one of the most abundant pollen plant» of its season, 
and the bees sometimes work on the tassels so freely as to give 
rise to the impression that it is a honey producer. Plant lice are 
