REPEODL'CTIVE ORGANS 



113 



75. Dispersal by locomotion. — I'lio coinmon method of 

 locomotioii is Ijy lueaus of movuljle luiirs {cilia) developed 

 upon the reprodtietive liody, whieh propel it through the 

 water (see Fig. 100). 

 Swininiiiig spores are 

 verj' common among 

 the alga;, and at least 

 one of tlio gametes 

 in algie, moss-plants, 

 and fern-jilants has 

 the power of swim- 

 ming Ijv means of 

 cilia. 



70. Dispersal by 

 water. — It is ver}- 

 common for repro- 

 ditctive hodies to be 

 transported hy cur- 

 rejits of water. The 

 spores of many water 

 jilants of all groups, 

 not constructed for 

 locomotion, are thus 

 floated ahout. 1'his 

 method of transfer is 

 also Yer-\' common 

 among seeds. Many 

 seeds are buoyant, or 

 become so after soak- 

 ing in water, and 

 may be carried to 

 great distances by 



currents. For this reason the plants growing iipon the 

 banks or flood-plains of streams may have come from a 

 wide area. Many seeds can even endure prolonged soak- 

 ing in sea-water, and then germinate. Darwin estimated 



Fli 



i. 1V2. The upper fi^ire to the left is ap opening 

 pod of fire^veed discharging its plumed seeds. 

 Tlie lower figiire represents the seed-like fruits 

 of CUmatU with their long tail-like plumes. — 

 After Kekner. 



