170 Field, Forest, and Wayside Flowers 
As grass-pollen is carried about among the blos- 
soms by the wind much of it is liable to be 
dropped and wasted. 
Fic. 43.—Sand-pur grass (Cenchrus tribuloides). 
a and 4, the bur ready to travel; c, the pair of flowers, 1 staminate and 1 perfect. 
(From Bulletin No. 7 of the U.S. Department of Agriculture, ‘‘ American 
Grasses.”’) 
In some species Nature makes good this loss 
beforehand by furnishing a double supply of the 
life-giving grains. 
