DISPERSAL OF SEEDS 



175 



seeds are transported. Nuts are buried by squirrels for food ; but 

 if they are not eaten, they may grow. The seeds of many plants 

 are blown on the snow. The old stalks of weeds, standing through 

 the winter, may serve to disseminate the plant. Seeds are carried 

 by water down the streams and along shores. About woollen mills 

 strange plants often spring up from seed brought in the fleeces. 

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

 Such plants are "tumbleweeds." Examples are Russian thistle, 

 hair grass or tumblegrass (Panicum capillare), cyclone plant 

 (^Cycloloma platyphyllum), and white amaranth {Amara7itus 

 alius). About seaports strange plants are often found, having 

 been introduced in the earth that is used in ships for ballast. 

 These plants are usually known as " ballast plants." Most of them 

 do not persist long. 185. Plants are able to spread themselves by 

 means of the great numbers of seeds that they produce. How 

 many seeds may a given elm tree or apple tree or raspberry bush 

 produce ? 



Fig, 253. — The Fruits 

 OF THE Cat-tail are 



LOOSENED BY WiND 



AND Weather. 



