222 



GROWTH AND WORK OF PLANTS 



ocean the seeds of many coastal plants are distributed to great 

 distances by the ocean currents. It has been found that many 



seeds will retain their vitality 

 after immersion in the salt water 

 of the ocean for three or four 

 weeks, and some will germinate 

 after prolonged immersion. 

 Darwin has shown by experi- 

 ment that about fourteen per 

 cent of the seeds of British 

 plants will bear immersion in 

 sea water for four weeks and 

 still germinate. The distribu- 

 tion of certain plants on near-by 

 islands, or in some cases on 

 islands quite remote, is some- 

 times explained by the ability of 

 the seeds to bear the prolonged 

 Fig. 175. soaking of an ocean voyage 



Seed pod of tick trefoil (Desmodium); at the f rrkrri r . ri ~ C V,,-.,. f 

 right some of the hooks greatly magnified. trom One snore t 



Hg. 176. 

 Seeds of Geum showing the hooklets where the end of the style is kneed. 



