186 ELEMENTARY STUDIES IN BOTANY 



tion of seeds are increased by dispersing them, and this 

 dispersal is provided for in various ways. Some seeds are 

 discharged mechanically ; many seeds (or fruits) are equipped 

 with tufts of hair (plumes) or wings for air-dispersal ; many 

 seeds (or fruits) are carried by currents of water, and in 

 the case of oceanic currents they may be carried great dis- 

 tances ; and many seeds (or fruits) are carried away from 

 the parent plant by animals. It must be remembered, 

 however, that many seeds and fruits fall to the ground from 

 the parent plant and are not dispersed at all. 



The process called seed-germination extends from the 

 starting of a dormant embryo into activity to the beginning 

 of food manufacture by the young seedling. The conditions 

 necessary for germination are moisture, free access of air 

 (oxygen), and a suitable temperature, and for most plants 

 this combination is best secured by burial in loose soil. The 

 entrance of water enables the dormant protoplasts to be- 

 come active again, and this activity is evidenced by respira- 

 tion. The first result of activity is the digestion of stored 

 food which then passes into the active protoplasts and be- 

 comes assimilated. As a result, the growth of the embryo 

 begins, the tip of the hypocotyl emerges from the seed, the 

 root is established, the plumule (and often the cotyledons) 

 are pulled out of the seed-coat, and when the seedling begins 

 to manufacture its own food, germination is over. 



