170 DISPERSAL OF SEEDS 



mills strange plants often spring up from seeds brought in the fleeces. 

 Sometimes the entire plant is rolled for miles before the winds. Such 

 plants are "tumble-weeds." Examples are Russian thistle (Fig. 113), 

 hair-grass or tumblegrass (Panicum capillare), cyclone plant (Cyclo- 

 loma platyphyllum), and white amaranth. About seaports strange 

 plants are often found, having been introduced with the earth that 

 is used in ships for ballast. These plants are usually known as "bal- 

 last plants." Most of them do not persist long. 



In some way, the seeds of every plant are dispersed, some far 

 and some near: discover these ways for any plant that you know. 



