HOW PLANTS ARE SCATTERED 



383 



Why do bur-bearing plants often carry their fruit until 

 late winter or early spring? 



What reason can be given for the fact that the burdock, 

 the cocklebur, the beggar's-ticks, the hound's-tongue, and 

 many other common burs, are among the most persistent 

 of weeds ? 



453. Uses of Stone Fruits and of Fleshy Fruits to the 

 Plant. Besides the dry fruits, of which some of the 

 principal kinds have been mentioned, there are many kinds 



FIG. 272. Burs. 



A, sticktights ; B, sticktiglits, two segments, magnified ; 

 C, burdock ; Z>, cockleburs. 



of stone fruits and other fleshy fruits (Sects. 242-247). 

 Of these the great majority are eatable by man or some of 

 the lower animals, and oftentimes the amount of sugar 

 and other food material which they contain is very con- 

 siderable. It is a well-recognized principle of botany, and 



