338 LUSSONS WITH PLANTS 



where wool is cleaned. All the types of hooks 

 and spines fit the seed or fruit to be carried by 

 animals, or even upon garments of men. The 

 reader will recall the sand -bur, clot -bur, burdock, 

 pitchforks, beggar's- ticks, and the like. Some 

 sticky seeds, as those of the mistletoe, are carried 

 on the feet of birds ; and the mud upon the 

 hoofs of horses and cows and the feet of birds 

 often contains seeds of various plants. 



417. The seeds of fleshy fruits are usually 

 bony, and although the fruits are eaten by birds, 

 or even by mammals, the seeds may not be injured. 

 Cherries, raspberries, blackberries, juneberries, are 

 widely spread in this manner by birds. In like 

 way, oats, maize and grasses may be disseminated 

 by herbivorous animals. One will often find such 

 plants springing up in woods along horse- trails. 



418. Many plants become the companions of 

 cultivated plants because their seeds cannot be 

 separated readily by the machines used for cleaning 

 seed. Thus the cockle (Figs. 143, 275, 276) lives 

 with the wheat because its seeds are about the same 

 diameter as the wheat seeds, and pass through the 

 screens; and the plant also has habits similar to 

 those of the wheat, whereby it is able to live 

 under the same conditions. Many weeds of lawns 

 and meadows are plants whose seeds cannot be 

 separated easily from the grass seeds. 



