114 



PLANT STUDIES 



that at least 

 fourteen per 

 cent, of the 

 seeds of any 

 country can re- 

 tain their vital- 

 ity in sea-water 

 for twenty- 

 eight clays. At 

 the ordinary 

 rate of move- 

 ment of ocean 

 currents, this 

 length of time 

 would permit 

 such seeds to 

 be transported 

 over a thou- 

 sand miles, 

 thus making 

 possible a very great range in distribution. 



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

 common methods of transport- 

 ing spores and seeds. In most 

 cases spores are sufficiently 

 small and light to be trans- 

 ported by the gentlest move- 

 ments of air. Among the 

 fungi this is a very common 

 method of spore dispersal (see 

 Fig. 106), and it is extensively 

 used in scattering the spores 

 of moss-plants, fern-plants (see 

 Fig. 45), and seed-plants. 

 Among seed-plants this is one fi«- "^ seed-iike fruits oi senecio 



° T 1 • . ^^'^^^ plumes for dispersal by air.— 



method of pollination, the After kerner. 



Fig. 113. A ripe dandelion head, showing the mass of 

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

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

 Kerner. 



