THE ANGIOSPERMAE 



1557 



wind for great distances over land. Over sea they are not so effective and 

 most of the pappose-fruited genera on oceanic islands have probably been 



Fig. 1419. — Tragopogon prntetisis. Longitu- 

 dinal section of the base of one of the rays 

 of the pappus, showing the puhinus-hke 

 tissue which causes the hygroscopic 

 folding and unfolding of the rays. {After 

 Hirsch.) 



carried there by birds or by man. If the pappus-borne fruit comes to earth, 

 it may be held by the friction of small prickles which are turned upwards 

 so that they catch easily, if the cypsela is dragged along the ground. These 

 grapnels are well seen in Taraxacum, while Senecio is furnished with sticky 

 slime glands which serve the same purpose of attaching the fruit to the 

 ground after it has once fallen there. The pappus may then blow away and 

 leave the fruit. Quite a large proportion of those seen blowing in the spring 

 airs have dropped their cypselas and are travelling light. 



Water Dispersal. The flotation of whole fruits by water most frequently 

 concerns indehiscent fruits. Some dehiscent fruits can float for some time 

 and dehisce in the water, the seeds, when released, either sinking or con- 

 tinuing to float by themselves. As we pointed out in the case of seed dis- 



