1 88 General Botany 



and water-absorbing organs. They do not take their nourish- 

 ment from the plants on which they grow. They carry on food 

 syntheses as other green plants do, but depend for their water 

 upon the evenly distributed rainfall and for their mineral sub- 

 stances upon dust and the decay of the bark on which they live. 



Epiphytes are pronounced xerophytes, for there is probably no 

 habitat in which it is more difficult to maintain a water balance 

 than the one in which they live. It is not surprising, therefore, 

 to find that among the epiphytic plants of the West Indies there 

 are several species of cactus. Among epiphytes there are many 

 species of ferns, and many species belong to two families of 

 flowering plants, the bromelias and orchids. The bromehas are 

 related to the pineapple and have leaves of the same form (Fig. 

 162). The orchids have flowers remarkable for their shapes and 

 colors, and have the distinction of being the highest-priced of all 

 flowering plants. The Spanish moss of Florida, a flowering plant, 

 is perhaps the best known of American epiphytes. It is an 

 extreme form and is devoid of roots. Spanish moss and some 

 other members of the bromelia family have peculiar scale hairs 

 through which water is absorbed directly by the leaves and stems. 

 The roots of many epiphytes contain chlorophyll and assist in the 

 manufacture of food. 



Roots in relation to bacteria. The roots of many plants have 

 bacteria or fungi growing about them or inside them. The best- 

 known crop plants belonging to this group are the clover , cow- 

 pea, and alfalfa ; their roots develop small nodules in which 

 certain kinds of bacteria change nitrogen of the air into nitrogen 

 compounds which may be used by the plants. More information 

 about these bacteria will be found in Chapter XXXVIII, on 

 " Bacteria and the Nitrogen Cycle " (page 396). 



Mycorhiza. A root which has a fungus regularly associated 

 with it is called a mycorhiza (Greek : myco, fungus, and rhiza, root) . 

 Many of our trees, like the oaks, maples, poplars, and conifers, 

 have fungi surrounding their roots. The beech tree, for example, 



