10 POLYPODIACEAE 



1. Pteris longifolia L. lieaves somewhat spreading; petioles 15-30 cm. long, 

 clothed below with pale brown scales; blades oblong-lanceolate, 3-6 dm. long; leaflets 

 linear, 4-10 mm. wide, entire, sessile: veins close, usually once branched. 



Peninsular Florida and the Keys, and Louisiana. Also widely distributed in the tropics. 



2. Pteris Cr^tica L. Leaves several ; petioles 15-30 cm. tall, straw-colored or 

 pale brown; blades 15-30 cm. long; leaflets usually 2-6 opposite pairs, sessile, the 

 sterile considerably broader and spinulose-serrulate, the lower pairs often parted 

 nearly to the base into 2 or 3 linear segments: veins parallel, simple or once forked. 



Peninsular Florida and the Keys. Also in tropical regions generally. 



3. Pteris multifida Poir. Leaves several ; petioles 15-22 cm. long, naked, pale 

 or brownish; blades ovate, 20-45 cm. long, 2-pinnatifid, the rachis with a wing 2-4 

 mm. wide at the top, thence narrowed downward; leaflets 6 or more pairs, opposite, 

 the upper simple, the lower with several elongated linear segments on each side; the 

 sterile portions spinulose-serrate. [P. serrulata L. f.] 



On old walls, South Carolina to Louisiana, escaped from cultivation. A native of China. 



9. PTERIDIUM Scop. 

 Coarse plants of open or partially shaded situations, with triangular to deltoid- 

 ovate compound leaf-blades. Sori marginal, linear, continuous, rising from a vein- 

 like receptacle connecting the ends of the forked free veins. Indusium double, the 

 outer conspicuous, formed by the reflexed margin of the leaf -blade, the inner obscure, 

 delicate, borne upon the vein-like receptacle. 



Ultimate segments of the leaf-blades approximate at the base. 1. P. aquilinum. 



Ultimate segments of the leaf-blades very narrow, 4-6 mm. apart at the base. 2. P. caudatum. 



1. Pteridium aquilinum (L.) Kuhn. Eootstock stout, woody, horizontal, ex- 

 tensively creeping underground. Leaves erect, sometimes 2 m. tall; petioles straw- 

 colored or brownish, 3-6 dm. long; blades 6-12 dm. long, triangular to deltoid-ovate, 

 usually subternate, the three divisions each 2-pinnate. [Pteris aqiiilina L.] 



In sunny places, throughout North America, Europe and Asia. Variable. P. aquilinum 

 pseudocaudatum Clute is a form occurring mainly along the coast from Massachusetts to the 

 Gulf states, with many of the pinnules linear and greatly elongated. Beacken. Brake. 



2. Pteridium caudatum (L.) Maxon. Leaves erect, 1-4 m. high, or some- 

 times taller; blades 3-4 pinnate; divisions pinnatifid, the ultimate segments narrow, 

 with recurved margins, remote, the larger with 1-12 similar but shorter segments. 

 [Pteris aquilina var. caudata (L.) Hook.] 



In sandy soil, Florida. Also in the West Indies. 



10. ADIANTUM L. 



Graceful plants of rocky hillsides, woods and ravines, with much-divided leaf- 

 blades. Petioles and their divisions slender or filiform, polished, usually dark colored 

 and shining. Sori appearing marginal, borne at the ends of the free forking veins 

 within the reflexed lobes (indusia) of the leaflets. Maidenhair Fern, 



Leaf-blades ovate-lanceolate or elongate-deltoid, pinnately compound, with a continuous rachis. 



Leaf-blades 1-2-pinnate: leaflets persistent. 1. A. Capillus-Veneris. 



Leaf-blades 3-4-pinnate; leaflets deciduous. 2. A. tenerum. 



Leaf-blades more or less orbicular, dichotomous, thus lacking a main 

 rachis, the elongated pinnae springing from the upper side of the 

 two usually recurved branches. 



Leaf-blades symmetrical, the two lateral branches equal; petioles, and 



leaf-tissue, nearly glabrous. 3. A. pedatum. 



Leaf-blades asymmetrical, the branches unequal; petioles, and leaf- 

 tissue (below), hispid. 4. A. hispidulum. 



1. Adiantum Capillus-V6nerls L. Eootstocks creeping, slender, chaffy with 

 light brown scales. Leaves numerous; petioles very slender, blackish, 7-22 cm. long; 

 blades ovate-lanceolate, 2-pinnate below, 1-pinnate above, membranous, commonly 

 drooping, 1.5-5 dm. long, 1-3 dm. wide at the base; leaflets cuneate-obovate or 

 rhomboid, the sterile ones incised, crenate or dentate-serrate: sori lunate or oblong. 



In ravines, preferring limestone, Virginia to Missouri, South Dakota and California, 

 south to Florida and Louisiana. Rare or local. Also in warm-temperate regions generally. 



2. Adiantum t6nerum Sw. Eootstocks creeping. Leaves several; petioles 3 

 dm. long; blades deltoid, 3-9 dm. long, 2-4 dm, wide, 3-4 pinnate; leaflets articu- 



