THE ROOT THE FORMS OF ROOTS 



35 



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

 plant .,. 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. 



