340 FILICES. Pcllaa. 



nate ; pinnjB several pairs, sessile, ascending or appresseJ to the rliacliis, very short, 

 often broader than long; pinnules 5 to 13 to a pinna, 3 to G lines long, crowded, 

 oblong-linear, greenish-glaucescent, niucroniilate, the edges much rolled back, making 

 the pinnules nearly terete, and covering the sori. — Syn. Fil. 2 ed. 477 ; Eaton, 

 Ferns of N. Anier. ii. 9, t. 47, fig. 4-6. Platyloma brachypterum, T. Moore, in 

 Gard. Chronicle, 1873, 141. PelUna Ornithopus, var. hrachyptera, Eaton, in Torr. 

 Bot. Bulletin, iv. IG, and Ferns of the Southwest, 322. 



Rocky places in the Sierra Nevada (Bolander, Mrs. Ames, Mrs. Austin, Kcllogq & Harford) ; 

 liassen's Peak (Lernmmi) ; Weaverville, Klceberger. In moist situations the growth is much larger 

 tlian in dry places. Platyloma helium, Moore, is probably a form of this species, but is not 

 known to me. The common plant so named is P. Ornithojms, modified by cultivation. 



-t- -)- Fronds trijnimate when fully developed. 



5. P. Ornithopus, Hooker. IJootstock short, thick, knotted, densely chaffy 

 with very narrow dark-brown scales : stalks clustered, rather stout and very rigid, 

 dark-purplish or almost black, polished, 2 to 10 inches long : fronds 4 to 12 inches 

 long, rigid, broadly ovate-lanceolate, tripinnate or in smaller plants bipinnate ; pri- 

 mary pinnaj spreading or obliquely ascending, linear, bearing from a few up to 16 

 pairs of usually trifoliolate, but varying to simple or to 5 - 7-foliolate, nearly sessile 

 pinnules, which are commonly 1| to 3 lines long, coriaceous, mucronulate, glauces- 

 cent beneath, roundish-quadrate in the very rare sterile fronds, and in the fertile 

 fronds having the margins rolled back to the midvein. — Sp. Fil. ii. 143, t. 116, A ; 

 Eaton, Ferns of the Southwest, 322, and Ferns of N. Amer. ii. 11, t. 47, fig. 7-10. 

 Allosorus andromeda'folius, Hooker, PL Hartweg. 342, not of Kaulfuss. A. mnat'o- 

 natus, Eaton, in Am. Journ. Sci. 2 ser. xxii. 138. P. mucronata, Eaton, Bot. Mex, 

 Bound. 233, in part. 



Dry exposed rocks, very common from Mendocino County to San Diego ; also on Guadalupe 

 Island, Palmer. The trifoliolate pinnules bear considerable resemblance to the three claws of a 

 bird's foot, whence the specific name. Small forms with bipinnate fronds have passed for P. 

 Wrkjhtiana, but do not form the massive rootstocks of the latter, and are said by Mr. AVrigiit to 

 cease their yearly growth long before it. 



6. P, densa, Hooker. Eootstocks rather slender, brandling and entangled, 

 chatfy with narrow blackish scales : stalks densely tufted, slender, wiry, dark-brown, 

 dull or polished, 3 to 9 inches long: fronds ovate or deltoid-ovate, 1| to 2| inches 

 long, closely tripinnate ; segments 3 to 6 lines long, nearly sessile, lance-linear, acute 

 or mucronate, in the rare sterile fronds sharply serrated, in the fertile fronds entire, 

 the margins narrowly recurved and bearing a paler distinct involucre. — Sp. Fil. ii. 

 150, t. 125, B; Eaton, Ferns of ^^. Amer. i. 77, t 11, fig. 1. OmjcMum densum, 

 Brackenridge, Fil. of U. S. Expl. Exped. 120, t. 13, fig. 2; Torrey, Pacif. E. Pep. 

 iv. 160. 



Clefts of rocks, not rare at elevations of 6,000 to 8,000 feet in the Sierra Nevada, from the Cas- 

 tle Mountains to the Yosemite; also in Oregon and in Wyoming Territory. The indusium is a 

 very delicate special organ, growing just within the margin of the segments. 



§ 3. Texture coriaceous, usually concealinrj the veins ; tdtimate segments broad 

 and flat, the involucre narroiv and at length hidden by the confluent sjio- 

 ra?z^Va. — Platyloma, Hooker & Baker. '{Platyloma, J. Smith.) 



7. P. Eridgesii, Hooker. Eootstock short, creeping, densely chaffy with nar- 

 row castaneous scales : stalks 3 to 6 inches long, clustered, terete, wiry, dark red- 

 dish-brown, smooth and shining : fronds as long as the stalks, linear-oblong, simply 

 pinnate ; pinna? 5 to 18 pairs, mostly opposite, subsessile, glaucous green, coriaceous; 

 sterile ones orbicular or subcordate, 4 to 5 lines long, rarely larger ; fertile ones 

 somewhat narrow, often at first conduplicate and apparently lunate : involucre nar- 

 row, formed of the whitish cartilaginous margin of the pinnre, soon flattened out and 

 exposing the sori confluent in a broad intraraarginal band. — Sp. Fil. ii. 238, and 

 iii, t. 142, B ; Eaton, Ferns of X. Amer. i. 327, t. 43, fig. 1-4. 



