SEED DISTRIBUTIOX 



313 



Frequently plants de- 

 velop special structures 

 which help to secure the 

 distribution of seeds 

 through the agency of 

 an animal. Fruits like 

 the burdock, for ex- 

 ample, are provided with 

 hooks which catch firmly 

 to a passing animal, and 

 the fruit is carried lomr 

 distances before the 

 seeds are dropped. 

 Other fruits, like the 

 cherry, have an edible 

 pulp which causes the 

 fruit to be picked up 

 and carried away. A 

 bird may fly with the 

 fruit to a fence post, 

 and there eat the pulp 

 and drop the seed. In 

 many cases, as in the 

 raspberry, the whole 

 fruit is eaten, but the 

 seeds are indigestible 

 and are carried far from 

 the parent plant before 

 they are thrown out by 

 the animal. 



Other fruits are fitted 

 for distribution by 

 water. In such cases 

 the fruit is surrounded 



Figure 334. — Milkweed Plant. 

 Distributing seeds. 



Figure 335. — Seed of Cotton. 



