THE STEUGGLE FOR EXISTENCE. 



201 



then blown along for great distances, until it is brought to a 

 standstill by a fence or other obstacle. The Russian thistle, 

 of which a small branch is shown in Fig. 184, forms, when 

 growing luxuriantly, roundish bushy masses, as much as 

 three feet high and six feet in diameter. These when dead 



Fig. 183. —Partly matured Panicle of Tiekle-Grass.' 



and dry, but loaded with seeds, drift before the wind in such 

 quantities that they often form sloping embankments reach- 

 ing to the tops of high fences. One such plant has been 

 estimated to carry with it as many as 200,000 seeds. 



1 Panwum capillare. 



