276 EVOLUTION OF PLANTS 



These tropical epiphytes represent many families of 

 flowering plants and also include a large number of 

 ferns. One family of the latter, the exquisite filmy- 

 ferns (Hymenophyllacese), are mainly epiphytic, and one 

 of the most charming sights of the tropical mountain 

 forests is exhibited by the trunks and branches of the 

 trees, covered with the dark-green, finely cut fronds of 

 these dainty ferns. In these dark forests, reeking with 

 moisture, everything is covered with a mass of epi- 

 phytic growths, even the leaves near the ground being 

 overgrown with lichens and creeping liverworts. 



Of epiphytic flowering plants there may be recognized 

 two categories — the lianas, or creepers, which, at first 

 at least, are rooted in the earth, but may later, by de- 

 veloping aerial roots, become truly epiphytic ; secondly, 

 the true epiphytes, or "air plants," such as many or- 

 chids and Bromeliacese, like the " Spanish moss," which 

 never are connected with the earth. These air plants 

 abound everywhere in the tropical forests, and some of 

 the epiphytic orchids are among the most beautiful 

 of all plants. These showy species are, however, 

 in a minority, as most of the tropical orchids are 

 by no means conspicuous. The peculiarly Ameri- 

 can family, the Bromeliaceae, includes a large num- 

 ber of curious epiphytes, some of which are showy 

 plants with spiky leaves and large clusters of bril- 

 liantly colored bracts or flowers. The best known 

 of these is the "Spanish moss," of the southern 

 United States, but most of them are strictly tropical 

 in their range. 



Many species of Ficus, or fig, are epiphytic, while 

 still others begin as epiphytes, germinating upon the 



