202 



GROWTH AND WORK OF PLANTS 



339. Dispersal of seeds by animals. In general there are two 

 ways in which animals distribute seeds: first, by eating the fruits; 



second, by seeds which cling to their 

 bodies. Edible seeds and fruits. In the 

 case of small seeds or grains which 

 are eaten by animals not all the seeds 

 are crushed and some pass through 

 the alimentary canal unharmed. In 

 the case of fruits eaten by animals 

 many have small seeds with hard seed 

 coats, and very few of these seeds are 

 crushed. The hard seed coats further 

 protect the embryo from the solvent 

 action of gastric juices, while in the 

 case of some seeds it is believed that 

 they germinate better after being sub- 

 jected to the action of various sub- 

 Fig. 163. stances while passing through the 



Fruit of burdock (Arctium lappa). alimentary canal of birdSj etc Fmits 



like the raspberries, blackberries, grapes, cedars, are eaten by 

 birds and other animals and the seeds de- 

 posited often far away from the place where 

 they were grown. Many such fruits have 

 bright colors and attractive flavors at the 

 time of ripening. Grapplers on seeds and 

 fruits. These are well known to nearly all 

 persons who tramp the fields or forest, and 

 may also be " picked up " along the high- 

 ways and in gardens. Hooks or barbs are 

 produced on parts of the fruit which cling 

 tenaciously to rough soft objects coming in 

 contact with them. Common among these 

 are the " beggar ticks," the akenes of one of 

 the composites (Bidens), which have barbs burdock - 

 on the two lateral prongs at one end of the flattened fruit. 

 In some sections these are called " devil's bootjack." Slender 



Fig. 164. 

 Hooks and akene of 



