THE ROOT 



77 



for instance, by bringing 

 about chemical changes 

 that might aid in the 

 work of nutrition. 



87. Epiphytes, or air 

 plants. In the proper 

 meaning of the word 

 these are not parasitic, 

 but use their host merely 

 as a mechanical support 

 to bring them into better 

 light relations. The 

 name, however, is loosely 

 applied to all plants that 

 find a lodgment on the 

 trunks and branches of 

 trees, whether parasites 

 or true epiphytes that 

 draw no nourishment 

 from the host. Not in- 

 frequently the latter is 

 killed by them through 

 suffocation, overweight- 

 ing, or the constriction 

 of the stems by close 

 clinging twiners. 



88. Aerial roots are 

 such as have no connec- 

 tion at all with the soil or 

 with any host plant, ex- 

 cept as they may lodge 



Upon the trunks and FlG - 90. A single strand of Tillandsia 

 ii . ,. usneoides, a rootless epiphyte belonging to the 



branches OI trees lOr a pineapple family ; better known as the " Span- 



support. In other than ish moss " that drapes the boughs , of A tree - so 



conspicuously in the warm parts of America. 

 purely epiphytic plants, Two-thirds natural size. (Photographed by C, 



which get all their nour- R ' Keefe -> 



