26o 



General Botany 



sperm, are inclosed in an ovulary commonly called a pod or cap- 

 sule, as in the bean, horsechestnut, hickory nut, and watermelon. 



V 



Wb 



Fig. 167. Fruits frequently transported by animals: A, beggar-ticks {Bidens) ; B, Spanish 

 needles {Bidens) ; C, sweet cicely {W ashingtonia) ; D, tick trefoil {Desmodium) ; E, cockle- 

 bur {Xanthium) ; and F, sand bur (Solanum). 



The term "angiosperm" means "hidden or covered seed." 

 The gymnosperm seed consists of an embryo, surrounded by 

 an endosperm (rich in carbohydrate, fat, and protein material), 

 and two seed coats. The embryo has several distinct cotyledons. 

 Separation of the seed. Seeds become free of the fruit or the 

 parent plant in various ways. Fruits of the akene type (sun- 

 flower, Spanish needle) are dry, one-seeded fruits, and are set 

 free at maturity by abscission from the receptacle. In the case 

 of some legumes, like the bean, the pods split open and the two 

 halves curl and twist, forcibly expelling the seeds. In the witch- 

 hazel the pod dries out at maturity and the outer wall shrinks 

 more than the inner, thus producing a tension. When a certain 

 tension is reached, the four-seeded capsule suddenly springs 

 apart, throwing the seeds several feet. In the walnut, coconut, 

 and many fleshy fruits (e.g., the apple) the seeds are set free only 

 by the decay of the fruit. The hard, resistant fruit wall of the 

 coconut is of advantage, since this palm is a common seashore 

 plant. The seeds may be carried for weeks by ocean currents 

 without injury. Orange and lemon seeds sometimes germinate 

 inside the ripe fruits. 



The dissemination of seeds. The wind is probably the most 

 important agent in transporting seeds. How far a seed may be 



