<y 
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 
Fie. 174.— Tufted 
Fruit of Fleabane. 
I Il 
» Fia. 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. 
