THE ANGIOSPERMAE 1519 



out when it lands on a wet place and it is only then that the capsules open 

 and the seeds are dropped. 



Fig. 1388. — Spinifex squnrrosus. Female in- 

 florescence which is detached from the plant 

 and rolls before the wind on the tips of the 

 long awns. About one-fifth natural size. 



Animal Dispersal (Zoochory). Distribution of seeds by animals occurs 

 in three ways. First, by animals feeding on fruits and swallowing the 

 seeds, which resist digestion and are passed with the excreta, uninjured 

 and sometimes actually more germinable than before. Secondly, by seeds 

 or fruits sticking to the outside of the animal, either by adhesive mucilage 

 or by means of hooks or spines. Sometimes small plants may be carried 

 about entire in this way. Thirdly, by seeds or small fruits being picked up 

 by the feet of an animal trampling in muddy soil. The wading birds are of 

 particular importance in this last method. 



Of all the groups of animals the birds are the most active in seed dis- 

 persal, because of the fruit-eating habits of so many of them and because 

 of the long distances they travel. They are the only animals capable of 

 carrying seeds far across the sea and they are responsible for many plants 

 reaching oceanic islands. The mammals come next in importance. Insects, 

 especially ants, are active transporters over short distances, while reptiles, 

 fish and molluscs may occasionally contribute their services. 



Seeds with hard testas are often very slow to germinate and there is 

 evidence that in some cases the hard covering is softened and germination 

 accelerated by passing through an animal's body. Seeds enclosed in fleshy 

 fruits, such as drupes or berries, or the fruit of the Fig and Strawberry, 

 which are commonly swallowed by birds, are those which seem to be most 

 improved by internal passage, germinating more rapidly and strongly than 

 without such treatment. In some instances this is possibly only due to the 

 removal of the flesh of the fruit, which seems to have an inhibiting action 

 on germination, since even the cleaned seeds germinate better than those 

 sown with the fruit flesh still adherent. 

 Q 



