THE ROOT— THE FORMS OF ROOTS 



35 



crevices and dark places of the wall or tree over which the 

 plant a^ climbs. The trumpet creeper (Fig. 36), true or 



English ivy, and poison ivy climb by 



means of roots. 



Fig. 37. — Aerial Roots of an Orchid. 



In some plants all the roots are 

 aerial ; that is, the plant grows above 

 ground, and the roots gather food 

 from the air. Such plants usually 

 grow on trees. They are known as 

 epiphytes or air-plants. The most fa- 

 miliar examples are some of the tropi- 

 cal orchids, which are grown in glass- 

 houses (Fig. 37). Rootlike organs of dodder and other 

 parasites are discussed in a future chapter. 



Fig. 36. — Aerial Roots 

 of Trumpet Creeper 

 or Tecoma. 



