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 

 branches of trees for a 

 support. In other than 

 purely epiphytic plants, 

 which get all their nour- 



Fk;. 90. — A single strand of TiUandsia 

 nxncoiden, a rootless epiphyte belonging to the 

 pineapple family ; better known as the " Span- 

 ish moss" that drapes the boughs of trees so 

 conspicuously in the warm parts of America. 

 Two-thirds natural size. (Photographed by C. 

 F. O'Keefe.) 



