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 

 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. The prickly 

 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 

 fields where they 

 This plant is shown 



Fig. 249. 

 Lactuca scariola. 



are unbidden as well as unwelcome guests. 

 in fig. 249. 



