tiaunis, Habiis, and Distribution, 21 



the spray of waterfalls, such delicate pellucid ferns as the filmy- 

 fern ( Trichomanes) and Pellcea gracilis may be sought. There 

 seems to be a direct connection between the environment- and the 

 texture of the fern. The last two mentioned grow in,vei-y damp 

 situations, and are pellucid and almost membranous. lCysto^,teris, 

 in somewhat drier situations is thinly herbaceous, while yjjf^/i?- 

 nium Trichomanes and Campiosorus, requiring less moisture^are 

 more firm, and form the transition to the next group which ccm- 

 tains ferns often leathery in texture. 



14. On dry cliffs we may look for the various species of 

 Woodsia, the cloak-ferns (Notkolcsna), the lip-ferns (Cheilantkes), 



and the cliff-brakes {Pellcea). All these are peculiarly fitted to 

 survive long periods of drought, and in some cases are specially 

 provided with structural appendages for this purpose. 



15. Only one of our native species is strictly aquatic, the 

 anomalous Ceratopteris thalictroides found in Southern Florida, 

 though Acrostichutn aureum is often found with its rhizoma rising 

 from the water of salt marshes. 



16. Among the epiphytic ferns are several species of Folypo- 

 dium, especially P. incanum, P. Scouleri, and P. aureum, the last 

 always being associated with the cabbage-palmetto {Sabal Pal- 

 metto). Vittaria and Nephrolepis are also of this class and are 

 frequently pendent from the same plant, tliough occasionally found 

 on other tree-trunks. Ophioglossum palmatum, another peculiar 

 tropical fern-like plant, belongs to the same list. -■■■ 



17. These principles of climatic distribution are more or less 

 modified by the geographical range of species, which must be con- 

 sidered in this connection. 



18. Geographical Distribution. — Ferns are found in all parts 

 of the world. The number of described species is not cer- 

 tainly known, and the uncertainty is largely- increased for the rea- 

 son that our best systematists do not agree as to what constitutes 

 a species. One of the best authorities describes 2646 species, 

 though several recognized American species are not mentioned, 

 and this is probably true of those of other countries.* 



From what has been said respecting the climatic conditions of 

 fern growth, we would naturally expect to find them most abun- 

 dant in countries where warmth and moisture predominate. These 

 conditions seem most completely met on tropical islands or in 



* Synopsis FUicitm, or, A Synopsis of All Known Ferns. By Sir W. J. Hooker and 

 J. G, Baker, Second Edition, London, 1874. 



