114 



PLANT STUDIES 



J*? J V 



'(^^K 



that at least 

 fonrteon per 

 cent, of the 

 seeds of any 

 country can re- 

 tain their vital- 

 ity in sea-water 

 f (.) r t w e n t y - 

 eiglit days. At 

 tlie ordinary 

 rate of move- 

 ment of ocean 

 currents, this 

 length of time 

 would ])ermit 

 such seeds to 

 he transported 

 o V e r a t h o u - 

 sand miles, 

 thus making 

 possihle a very great range in distrilnition. 



77. Dispersal of spores by air. — Tliis is one of the most 

 comnuiu methods of transport- 

 ing s])ores and seeds. In most 

 cases sp(n'es arc sufficiently 

 small and light to he trans- 

 ported liy the gentlest move- 

 ments of air. Among the 

 fungi this is a very common 

 method of spore dispersal (see 

 Fig. loo), and it is extensively 

 used in scattering the spores 

 of moss-phints, fern-plants (see 

 Fig. 4.5), and seed-plants. 

 Among seed-plants this is one ^'"- "■*• s«'d.iikc fmits of Senedo 



^ p -,,. . With plumes for diepereal by air.— 



method of poliiiuitioii, the After kkuner. 



Fig. 113. A ripe dandelion bead, sbovviiig the mass of 

 plameB, a few seed-like fruits with their plumes still 

 attached to the receptacle, and two fallen off.— After 

 Kkknek. 



