WATER SUPPLY OF EPIPHYTES 473 



fifty or a hundred years, reaching meantime a diameter of not 

 more than two inches, and then, on getting more light, shoots 



up into a large and valuable timber tree. 1 

 .^ 



449. Epiphytes. It is even easier for a plant to secure enough 

 sunlight iii a forest region by perching itself upon the trunk, 

 branches, or leaves of a tree than by climbing, as our wild grape- 

 vines and the great tropical lianas do. There is a large number 

 of such perched plants, or epiphytes (meaning upon a plant), par- 

 ticularly in such tropical forests as those of Fig. 39 and Plate 

 XIII. Epiphytic forms occur among many different groups of 

 seed plants and of spore plants, especially lichens. The stag- 

 horn fern, shown in Fig. 365, is a good example of an epiphyte. 

 Instances among seed plants are the so-called Florida or Spanish 

 moss (Plate III) and orchids like those in Fig. 13. 



450. Water supply of epiphytes. Epiphytes secure their 

 supply of water and dissolved salts in several different ways, 

 some through roots bv absorption from the moist bark on which 



O */ -L 



they grow, others by sending roots down until they reach the 

 earth, others by means of a network of aerial roots fully exposed 

 to the air,- -as in the orchid just mentioned,- -and still others 

 by means of leaves which function as roots. Some species, like 

 the Florida moss, absorb water very rapidly from dew or rains, 

 while others, as the stag-horn fern (Figs. 272, 365), and Til- 

 landsia butbosa, a relative of the Florida moss, hold water in 

 reservoirs at the bases of the leaves, with or without the aid of 

 spongy decaying vegetable matter. From the great vicissitudes 

 in their water supply most epiphytes among seed plants possess 

 xerophytic characteristics. 



1 See the Primer of Forestry, Part I. United States Department of Agri- 

 culture, 1899, pp. 33-35. 



