456 FILICES. 



with 3 — 6 subulate wliitish awned teeth. Spikes ovoid capitate, 2 — 3-liiie« 

 long, blackish. Torr. N. Y. Fl. The smallest of the genus. 



Smallest Rough Horse-tail. 



Order CXLIX. FILICES.— Ferns. 



Fructification only of one kind on the same individual. 

 Spore-cases sometimes in distinct spikes or racemes, but usu- 

 ally collected into clusters of various shapes, (sori,) arising 

 from veins on the imder surface of the leaf or frond ; either 

 pedicellate, with the stalk passing round them- in the form of an 

 elastic ring, or sessile and destitute of such a ring ; and either 

 naked, or covered with an involucre, (indusium.) Spores very 

 minute. — Leafy plants, producing a rhizoma which is mostly 

 creeping, but sometimes arborescent. Fronds coiled up before 

 expansion, simple or variously branched and divided. 



I. PoLTPODE^:. Spore-cases stalked, furnished with an articulated 

 elastic more or less complete ring, opening transversely and irregularly. 



1, POLYPODIUM. Z.wm.— Polypody. 



(From the Greek ttoXv? , many, and ttoxij, ttoJo? , a/oof ; from the numerous feet- 

 like branches of the root-stock.) 



Sori roundish, scattered on various parts of the lower surface 

 of the frond. Indusium none. 



* FroTid pinnatifid. 

 1. P. vulgare var. Americanum Hook. : frond smooth, deeply pinnatifid; 

 segments linear-oblong, obtuse, crenate-serrulate, the upper ones becoming 

 gradually smaller ; sori large, distinct. P. Virginianum Witld. 



Rocky woods. Arct. Amer. to Car. W. to Miss. July, %. — Rhizoma creep- 

 ing, clothed with brownish chaffy scales. Fronds 6—10 inches long, U — 2 inches 

 wide, growing in thick patches ; segments mostly alternate. Sori large, in 

 double rows on the back of each segment, at first distinct and yellowish, at 

 length in contact and dark colored. According to Torrey, the American plant 

 differs from the European only in the fronds being narrower and more oblong, 

 ♦he segments more distant, and the sori nearer the margin. 



Common Polypody. 



** Frond bipinnatifid. 



2? P. hexagoTwpterum Mich.: stipe smooth; frond bipinnatifid, slightly 

 pubescent, the lowest divisions deflexed ; segments lanceolate, obtuse, ciliate, 

 crenate or toothed ; the lowest pairs adnate-decurrent, connected by an ob- 

 long somewhat hexagonal wing ; sori minute. 



Moist woods. Can. to Car. July. %.. — Stipe 12 — 15 inches long, slender, 

 smooth. Frond triangular in its outline, the base 6—9 inches wide, and offen 

 exceeding the length. Sori very small, roundish, distinct, marginal, in 1 — 3 

 rows. Winged Polypody. 



