THE FRUIT. 



189 



It is an interesting and well-established fact that a good 

 many birds, especially bluejays, bury large numbers of acorns 

 and nuts which they intend to consume later, 

 and that they leave a considerable portion of 

 these deposits untouched. In this way large 

 numbers of trees are annually planted. 



228. Burs. — A large class of fruits is 

 characterized by the presence of hooks on 

 the outer surface. These are sometimes out- 

 growths from the ovary, sometimes from the 

 calyx, sometimes from an involucre. Their 

 office is to attach the fruit to the hair or fur 

 of passing animals or to. the clothing of 

 people who come in contact with it. Often, as in cleavers. 

 Fig. 177, the hooks are comparatively weak, but in other 

 cases, as in the cocklebur, Figs. 178, 179, and still more in 

 the Martynia, the fruit of which in the green condition is 



Fig. 174, — Tufted 

 Prult of Fleabane. 



n 



Pig. 175. — Seeds with Tufts of Hair. 

 I, milkweed ; II, willow-Herb. 



much used for pickles, the hooks are exceedingly strong. 

 Cockleburs can hardly be removed from the tails of horses 

 and cattle, into which they have become matted, without 

 cutting out all the hairs to which they are fastened. 



