692 FILICES. (FERNS.) 



18. TRICHOMANES, L. FILMY FERN. 



Sporangia with a transverse entire ring, sessile on a cylindrical receptacle 

 which is produced from the end of a vein and enclosed in a funnel-form or 

 cup-shaped involucre of the same substance with the frond. Fronds very 

 thin and pellucid, often consisting of a single layer of cells. (An ancient 

 Greek name for some fern.) 



1. T. radicans, Swartz. Fronds very delicate, oblong-lanceolate in out- 

 line (4-8' long, 6- 18" wide), bipinuatifid ; rhachis narrowly winged ; pinna? 

 triangular-ovate, the divisions toothed or again lobed ; involucres tubular- 

 funnel-shaped, margined, the mouth truncate ; receptacle often much exserted. 

 On moist and dripping sandstone cliffs, Ky., and southward ; rare. Though 

 the fronds are so very delicate, yet they survive for several years ; they begin 

 to fruit the second or third year, and thereafter the receptacle continues to 

 grow and to produce new sporangia at its base. (Eu.) 



19. SCHIZJEA, Smith. (PI. 20.) 



Sporangia large, ovoid, striate-rayed at the apex, opening by a longitudinal 

 cleft, naked, vertically sessile in a double row along the single vein of the nar- 

 row divisions of the pinnate (or radiate) fertile appendages to the slender and 

 simply linear, or (in foreign species) fan-shaped or dichotoraously many-cleft 

 fronds (whence the name, from ax'ifa, to split). 



1. S. pusilla, Pursh. Sterile fronds linear, very slender, flattened and 

 tortuous; the fertile ones equally slender (" wide), but taller (3-4' high), 

 and bearing at the top the fertile appendage, consisting of about 5 pairs of 

 crowded pinna (each 1-1-J-" long). Low grounds, pine barrens of N. J. ; 

 very local. Sept. (Also in Nova Scotia and Newf.) 



20. LYGODIUM, Swartz. CLIMBING FERN. (PI. 20.) 



Fronds twining or climbing, bearing stalked and variously lobed (or com- 

 pound) divisions in pairs, with mostly free veins ; the fructification on separate 

 contracted divisions or spike-like lobes, one side of which is covered with a 

 double row of imbricated hooded scale-like indusia, fixed by a broad base to 

 short oblique veinlets. Sporangia much as in Schizaea, but oblique, fixed to 

 the veinlet by the inner side next the base, one or rarely two covered by each 

 indusium. (Name from \vy<a8r)s, flexible.) 



1. L. palmatum, Swartz. Very smooth; stalks slender, flexile and 

 twining (1-3 long), from slender running rootstocks; the short alternate 

 branches or petioles 2-forked; each fork bearing a round-heart-shaped pal- 

 mately 4-7-lobed frondlet; fertile frondlets above, contracted and several 

 times forked, forming a terminal panicle. Low moist thickets and open 

 woods, Mass, to Va., Ky., and sparingly southward ; rare. Sept. 



21. OSMUND A, L. FLOWERING FERN. (PI. 20.) 



Fertile fronds or fertile portions of the frond destitute of chlorophyll, very 

 much contracted, and bearing on the margins of the narrow rhachis-like divis- 

 ions short-pedicelled and naked sporangia ; these are globular, thin and reticu- 

 lated, large, opening by a longitudinal cleft into two valves, and bearing near 



