POLYPODIACEAE. 



427 



margin. Veins free. [Greek, referring to the shape of the indusium.] About 

 12 species, natives of tropical and warm-temperate regions. Type species: 

 Polypodium exaltatum L. 



1. Nephrolepis exaltata (L.) Schott. 

 Sword-fern. (Fig. 467.) Petioles 4'-6' 

 long; leaf -blades 3° long or less; pinnae 

 sessile, lanceolate, sometimes crenulate, 

 l'-3' long, the upper side auricled at the 

 base, the lower rounded, the rachis quite 

 hairy; sori almost marginal, covered with 

 firm distinctly reniform indusia. [Poly- 

 podium exaltatum L. ; Aspidium exalta- 

 tum Sw.] 



Frequent in the marshes and on shaded 

 rocks between Harrington Sound and Castle 

 Harbor ; and on Abbot's Cliff. Native. 

 Florida and the West Indies. 



Lefroy records the introduction by 

 him of many species of ferns for '.-ultiva- 

 tion, and ferneries have been maintained 

 by other residents from time to time, 

 but few species will flourish without care- 

 ful attention, much moisture and proper 

 protection. Jones, in 1873, mentions a 

 number of species, evidently in cultiva- 

 tion at that time. 



Order 2. SALVINIALES. 



Aquatic or mud-inhabiting' herbs, \vitli horizontal or creeping: stems, 

 or floating. Leaves various, sometimes filifonu, or blades entire, lobed or 

 4-foliolate. Spores of two kinds (microspores and macrospores), con- 

 tained in sporocarps. Macrospores germinating into simple prothallia 

 which bear archegones, the microspores forming still simpler prothallia 

 bearing- antherozoids. 



Family 1. SALVINIACEAE Reichenb. 

 Salvinia Family. 

 Small floating plants with a more or less elongated and sometimes 

 branching axis bearing 2-ranked leaves. Sporocarps soft, thin-walled, 

 borne 2 or more on a common stalk, in the axils of the submersed leaves, 

 1-celled, with a central often branched receptacle, which bears macro- 

 sporanges containing a single macrospore or microsporanges containmg 

 numerous microspores. The family consists of two genera. 



1. SAIiVINIA A dans. 

 Floating annual plants with slender stems bearing rather broad 2-ranked 

 floating leaves. Sporocarps globose, depressed, 9-14-sulcate, membranous, ar- 

 ranged in clusters, 1 or 2 of each cluster containing 10 or more sessile macro- 

 sporanges, each containing few macrospores, the others containing numerous 



