THE STRUGGLE 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 
Fie. 183. — Partly matured Panicle of Tickle-Grass.1 
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 Panicum capillare. 
