220 



GROWTH AND WORK OF PLANTS 



352. Dispersal of seeds by animals. In general there are 

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



fruits; second, by carrying 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 un- 

 harmed. 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 

 subjected to the action of various 

 substances while passing through the 

 alimentary canal of birds, etc. Fruits 

 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 

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

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



Fig. 172. 

 Fruit of burdock (Arctium lappa). 



Fig. 173. 



Hooks and akene of 

 burdock. 



