110 



A PRIMER OF BIOLOGY 





either from the wall of a single seeded fruit, as in 

 Clematis, or from the wall of the seed itself, as in the 

 willow. Obviously the same 

 adaptations will be effective in 

 relation to water dispersal, pro- 

 vided the protective arrange- 

 ments are such as to shield the 

 embryo from injury from water, 

 be it fresh or salt. 



Animals -are by far the most 

 effective agents in seed dispersal. 

 Thus seeds and fruits may be 

 provided with hooks or spines 

 which stick to the fur or feathers, 

 1^ as in the case of the burdock, 



hedge-burr, medic, &c. (Fig. 55). 

 \ Succulent fruits, on the other 



hand, appeal to the desire for 

 food on the part of the animal. 

 In some cases the fruit is re- 

 moved from the plant and carried 

 to a distance before being eaten. 

 The seeds, then rejected, are thus 

 sown far away, it may be, from 

 their place of origin. In other 

 cases the fruit is swallowed 

 entire and passes through the 

 intestine, but the embryos are 

 protected from the action of the 

 digestive juices of the animal's 

 FIG. 57. Fruit of Gera- alimentary canal, either by the 

 nium before and after testa O r by a hardening of the 



bursting. 



innermost laver of the fruit wall 



as in the cherry (Fig. 56). 



In other cases still, the plant itself arranges for the 



