SEED DISTRIBUTION. 



295 



the seeds are provided with ' ' floats, " " parachutes, ' ' or winged 



devices which buoy them up as they are whirled along, often 



, . miles away. In 



Hjl/Ly ' late spring or early 



summer the pods 

 of the willow burst 

 open, exposing the 

 seeds, each with a 

 tuft of white hairs 

 making a mass of 

 soft down. As the 

 delicate hairs dry, 

 they straighten out 

 in a loose spread- 

 ing tuft, which frees 

 the individual seeds 

 from the compact 

 mass. Here they 

 are caught by cur- 

 rents of air and 

 float off singly or 

 in small clouds. 



461. Theprickly 

 lettuce. — In late 

 summer or early 

 autumn the seeds 

 of the prickly let- 

 tuce (Lactuca sca- 

 riola) are caught 

 up from the road- 

 sides by the winds, 

 and carried to 

 ¥ f Fig - 249 -. . fields where they 



Lactuca scanola. J 



are unbidden as well as unwelcome guests. This plant is shown 

 in fig. 249. 



