DISPERSION OF SEEDS 145 



may all die, and the plant fail to leave offspring 

 behind. On the other hand, if the ground be favour- 

 able, so many plants may spring up within the re- 

 stricted area that a hard struggle for life ensues 

 amongst them, which may end in their total exter- 

 mination. To provide against these and other con- 

 tingencies, seeds and fruits (enclosing seeds) are found 

 provided with varied devices for their dispersion, so 

 that, on falling on varied areas with varied conditions, 

 some are sure to come across favourable conditions 

 of germination and growth, and produce healthy 

 offspring, while others, meeting with unfavourable 

 conditions, may not germinate at all, or, if they do 

 germinate, produce only weaklings, which soon suc- 

 cumb in the struggle for existence. 



The agents for the dispersion of seeds are nearly the 

 same as those for the pollination of flowers. Thus 

 they are dispersed by currents of air and water; by 

 the forcible discharge from fruits which split elasti- 

 cally; by railroads and ships; and by animals, in- 

 cluding man. 



For the purpose of dispersion through air, seeds 



must remain floating in the air for some time, so that 



the currents of air may take them to distant places 



before they fall to the ground. In order to remain 



so floating they must be very small and light, and are 



often provided with hairs or similar appendages. For 



example, the seeds of kapas-tula or Cotton, and 



shimool-tula or Silk-cotton, are covered with hairs 



which are outgrowths of the testa ; the seeds like those 



of karabi and akanda (see fig. 123), in fact the seeds 



of most Apocynacece and AsclepiadacecB, are provided 



with a crown of hair (coma) ; the seed-like fruits of 



CompositcB (see fig. 81) are provided with a crown of 



hairy growths (the pappus) or teeth; the seed-like fruits 

 (oiMs) 11 



