1124 



EPIPHYLLUM 



EPIPHYTES 



the throat greenish yellow, tube very short, the limb 

 wide-spreading, 4-6 in. diam. B.R. 1331. Not known 

 in the wild state. 



BB. Style white: fis. smaller than the last. 

 phyllanthoides, Sweet (Phyllocdctus phyllanthoides, 

 Link). Branches at length hanging, cylindrical at base, 

 lanceolate above; serratures obtuse; middle and side 

 ribs evident; bristles few: fl.-tube 2 in. long or less, with 

 spreading scales, the limb somewhat longer, often 

 striate. S. Mex. J. N. ROSE. 



EPIPHYTES. Literally "air plants:" those plants 

 that do not grow in earth or water, but are supported 

 in air on trees or other objects and usually drawing no 

 organic nourishment from such object or support. 



True epiphytes are widely distributed in all climates, 

 but it is in the moist tropics that they become so numer- 

 ous and conspicuous as to arouse the special interest 

 and enthusiasm of the serious student as well as of the 

 traveler or casual observer. One thinks of epiphytes 

 as growing upon trees, and trees are usually the sup- 

 porting plants. The term merely signifies that ecologi- 

 cal type that has the habit of growing upon other 

 plants, although in this account it is not the purpose to 

 discuss such seaweeds or other algse as grow upon larger 

 plants in the water. The word epiphyte also involves 

 a contrast with parasite, the latter denoting that 

 nourishment and water are derived from the living 

 tissues of the supporting plant or host. The epiphytic 

 habit implies no particular 

 method of nutrition, and the 

 epiphytes are entirely indepen- 

 dent of the nutrition of the 



1402. Epiphyllum Ackermannii. ( X K) 



supporting plant. This habit is not restricted to a 

 single class, or to a few families of plants, although in 

 some families many representatives of the type have 

 been developed, while in related families there may be 

 none. The seed plants are represented by many species 

 of tropical orchids, arums, bromeliads, and numerous 

 others; lycopods, ferns, mosses and liverworts all con- 

 tribute many examples; and in the lower groups of 

 plants the lichens are in some regions dominantly 

 epiphytic. 



The luxuriant tropical rain-forest is regarded as the 

 climax in development of vegetation. In describing 

 this type, Humboldt declared that "forest is piled upon 

 forest." Under such conditions the trunks and branches 

 are clothed with larger epiphytes, and the leaves of 

 some species accommodate algse and lichens. It is in 

 the South American tropical forests that the better 

 known of our greenhouse epiphytes are native. Orchids, 

 bromeliads, and arums are among the most abundant. 

 In the Javanese forests, the wealth of species is great, 

 but mosses, ferns and lycopods are particularly numer- 

 ous, and these are accompanied by some interesting 

 species of Ficus, epiphytic for a time, and by the 

 striking Rhododendron javanicum, among others. In the 

 mountain forests of tropical regions there are, as 

 epiphytes, representatives of several families of ferns, 

 likewise many mosses and lichens. The dicotylous and 

 certain coniferous forests of Europe and America harbor 

 a few mosses and liverworts and numerous species of 

 lichens. A conspicuous epiphyte of the southern states, 

 as well as of tropical America is the long or Florida 

 moss, Tillandsia usneoides, the extremest epiphyte 

 among the Bromeliacese. Accompanying this, the 

 common polypody fern is also found on trees. Going 

 northward, the total number of epiphytic lichens may 

 decrease, but several of the larger forms seem to become 

 more abundant and some of the moss-like usneas 

 extend to the northernmost latitude of 

 tree growth. 



The habit of growing upon trees ren- 

 ders epiphytes subject to an inconstant 

 water-supply. On this account the larger 

 and more delicate epiphytes are restricted 

 to regions constantly moist. Even in the 

 moist forest, the species less resistant to 

 drying out are found on the lower branches, 

 and those more resistant maintain them- 

 selves higher up, so that there is a dis- 

 tribution in strata, analogous to the lateral 

 distribution of species about the edge of 

 a pond. In general, however, there is ex- 

 posure to drying out, and, as might be 

 anticipated, these plants exhibit the struc- 

 tural characteristics of xerophytes (dry- 

 land plants). Many of them are modified 

 so that transpiration is reduced, and they 

 are able to withstand considerable desic- 

 cation. Among greenhouse forms this is 

 notably true of many orchids and lichens. 

 Moreover, many species of orchids possess 

 special tissues to which water is trans- 

 ported and there accumulated as a "re- 

 serve" supply. Leaf-tissues may function 

 in this way, but usually more important 

 are the bulb-like enlargements of the 

 stems. 



Of special interest are the organs of 

 absorption of certain epiphytes. Aerial 

 roots are characteristic of tropical arums 

 and orchids. The typical air-root is pro- 

 vided with an outer cylinder of tissue, the 

 velamen, derived from the epidermis, con- 

 sisting at maturity of dead cells capable of 

 taking up liquid water and substances in 

 solution like a sponge. From these roots 

 as capillary reservoirs, the supply is gradu- 



