ECOLOGY OF FRUITS 



193 



238. Tumbleweeds. — Late in the autumn, fences, par- 

 ticularly on prairie farms that are not carefully tilled, 



often serve as lodging-places for 

 immense numbers of certain dried- 

 up plants known as tumbleweeds. 

 These blow about over the level 

 surface until the first snow falls 



Fig. 14-1. Eussian Thistle. 



and even after that, often 

 traveling for many miles be- 

 fore they come to a stop, and 

 rattling out seeds as they 

 go. Some of the commonest 

 tumbleweeds are the Russian 

 thistle (Fig. 144), the pig- 

 weed (Amarantus grcecisans), the tickle-grass (Fig. 145), and 

 a familiar pepper-grass (Lepidium). In order to make a 



Fig. 145. Panicle of Tickle-Grass, 

 a Common Tumbleweed. 



