MAXONIA, A NEW GENUS OE TROPICAL AMERICAN 



FERNS 



By carl CHRISTENSEN. Copenhagen 



While working' with the genus Dryopteris I have had for examina- 

 tion several specimens of a fern which in my Index Filicum was 

 called Polystichum apiifolium (Swartz) C. Chr. and later was re- 

 ferred to Dryopteris by Maxon.' Considering, however, that it 

 differs widely from the common type of Dryopteris. Maxon placed 

 it in a special subgenus, for which he created the new name Peisma- 

 podium. To me it was evident, upon very slight examination of a 

 full-grown fertile specimen, that this fern should certainly not be 

 placed in Polystichum, although in some respects it resembles P. 

 adiantifonnc ; its proper place seemed to be in the genus Dryopteris 

 and its alliance with such species as D. amplissima, D. macrostegia, 

 D. ochroptcroidcs, and a few others, which together form a very 

 distinct group of Dryopteris characterized by a certain polystichoid 

 habit and, generally, leathery leaves. On closer examination I have 

 foundj however, that in essential characters P. apiifolium is very 

 different from the species mentioned, and that it represents an 

 apparently monotypic genus of very great interest, since it is, in fact, 

 a connecting link between Polybotrya and the group of Dryopteris 

 species just mentioned. 



The plant under discussion usually has decidedly dimorphic leaves, 

 as has Polybotrya. They are borne on a very thick rhizome (2 to 

 3 cm. in diameter), which is clothed throughout with long, narrow, 

 rufous scales and which climbs on trees (and cliffs?) as do those of 

 Polybotrya osmundacea, Polystichum adiantiformc, and Davallia 

 canariensis. Within the genus Dryopteris a. similar rhizome is un- 

 known, although that of D. amplissima has a certain resemblance to 

 it. The sterile leaves are tri-quadripinnate, leathery, and of the 

 same general habit as those of the species with which I have com- 

 pared P. apiifolium. They are destitute of scales and hairs on the 



^ Contr. U. S. Nat. Herb. 13: 39. 1909. 



• Smithsonian Miscellaneous Collections, Vol. 66, No. 9 



