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CELL INTELLIGENCE THE CAUSE OF EVOLUTION 



wings are developed by the fruit of maples and elms, and 

 by the seeds of catalpa and its allies. Plumes and tufts 

 of hair are developed by the seed-like fruits of thistle, 

 dandelion and many of their relatives and by the seeds of 

 milkweeds, willow herbs, etc. On plains or level 

 stretches, where winds are strong, a curious habit of seed- 



FIG. 34. Seed 



r -for parachutes. 



dispersal has been developed by certain plants known as 

 tumbleweeds or field rollers. These plants are profusely 

 branching annuals with a small root system in light or 

 sandy soil. When the work of the season is over and 

 the absorbing rootlets have shriveled, the plant is easily 

 broken from its roots by a gust of wind, and is trundled 

 along the surface like a light wicker ball, the ripe seed 

 vessels dropping their seeds by the way. In case of an 



