FILICES. 121 



very minute, divided almost to the centre into a few beaded 

 iiairs. Arizona, Utah, Colorado, Oregon, and northward. 



6. W. Mexicana Fee. Stipes 2' — 3' long, smoothish or 

 with a few scattered scales ; fronds 3' — 9' long, lanceolate ; 

 pinnae sub-opposite, triangular-lanceolate, pinnately divided 

 into finely-toothed segments, the teeth in young fronds ending 

 in delicate, semi-transparent, ciliated tips ; sori near the mar- 

 gin, broad, confluent ; receptacles dot-like, scales of indusium 

 four, laciniate, narrow, dividing at the end into articulated 

 hairs ; sporangia nearly sessile. Arizona, New Mexico. 



§2. Hypopeltis Torr. Iitdushun conspicuous, at Jlrst en- 

 closing the sporafigmm, but early opening at the top and splitting 

 ijtto several spreading jagged lobes. 



7. W. obtusa (Spreng.) Torr. Stipes 3'— 6' long; fronds 

 broadly lanceolate, minutely glandular-hairy, 6' — 12' high, 

 nearly bipinnate; pinnae rather remote, triangular-ovate or ob- 

 long, pinnately parted ; segments oblong, obtuse, crenately 

 toothed, the lower ones pinnatifid ; veins forked. {^W. Perrin- 

 iana H. & G., Aspidium obtusum Willd., Cheilanthes crenata 

 Kunze, Hypopeltis obtusa Torr.) Smaller and more glandular 

 forms are var. glandulosa Eaton ( W. PlummercE Lemmon). 

 New England to Kentucky, Kansas, and Arizona. 



XXV. DICKSONIA L'Her. 



Sori small, globular, marginal or intra-marginal. Sporangia 

 borne in an elevated, globular receptacle, enclosed in a mem- 

 branous, cup-shaped indusium, which is open at the top, and 

 on the outer side partly adherent to a reflexed toothlet of the 

 frond. Named for James Dickson, an English botanist, 1738- 

 1822. Includes about 50 species, more than half of which are 

 arborescent. 



§ SiTOLOBIUM J. Sm. 



I. D. punctilobula (Michx.) Gray. Rootstock slender, 

 creeping, naked; stipes stout, chafBess ; fronds 1° — 24° long, 

 5' — 9' broad, ovate-lanceolate and pointed, usually tripinnatifid ; 

 pinnae lanceolate, pointed ; pinnules cut into oblong and ob- 

 tuse cut-toothed lobes ; rachis and under surface minutely 

 glandular and hairy; sori minute, each on a recurved toothlet, 

 usually one at the upper margin of each lobe. {D. punctiloba 



