498 FERN FAMILY. 



17. CYSTOPTERIS. (Greek for bladder fern, alluding to the thin, 

 sometimes inflated indusium.) Species few, mostly northern. 



C. fragilis, Bernh. Shaded or moist, rocky places, common 1ST. ; fronds 

 very delicate, 4'-8' long, with slender stalks, oblong-ovate, twice-pinnate ; 

 pinnae with a narrowly margined rhachis ; pinnules oblong or ovate, 

 toothed or incised, very variable ; indusium pointed at the upper end. 



C. bulblfera, Bernh. Wet places, oftenest in ravines, from N. Car., 

 N. ; fronds l°-3° high, 3'-6' wide at the base, narrowed above and much 

 elongated, twice pinnate, bearing scattered bulblets beneath ; pinnules 

 oblong, obtuse, toothed or pinnatifid ; indusium roundish, truncate on 

 the upper side. 



18. NEPHROLEPIS. (Greek: kidney, scale, referring to the shape 

 of the indusium.) 



N. exaltata, Schott. Fla. and the tropics, and one of the commonest 

 ferns of conservatories ; fronds l°-6° long and very narrow ; the pinnae 

 crowded, lanceolate, entire or slightly crenulate, the upper side auricled 

 at the base ; indusium kidney-shaped. 



N. darallioldes, Kunze. Popular conservatory fern from E. Indies, 

 with a stoloniferous base ; and pinnate fronds 2°-4° long and 1° broad, 

 on rather short, strong stipes ; pinnae 4'-6' long and J'-l' broad, lanceo- 

 late, the lower ones opposite and sterile and serrate, the upper ones fer- 

 tile and longer and narrower, more deeply toothed. A common form is 

 var. ftJbcans, in which the ends of the upper pinnae, and often of the 

 frond itself, are deeply 2-oo -forked. 



19. WOODSIA. (For Joseph Woods, an English botanist.) Several 

 species occur in our limits, the following being the commonest. 



W. obtusa, Torr. Eocky places, from Car., N. ; fronds 6'-18' high, 

 slightly glandular, broadly lanceolate, pinnate, with ovate or oblong, deeply 

 pinnatifid or again pinnate divisions ; lobes oblong, obtuse ; indusium at 

 first closed, opening into a few ragged lobes. 



W. Ilve'nsis, R.Br. Exposed rocks, common N., and along the Alle- 

 ghanies ; forms large tufts ; fronds 4'-8' high, rusty chaffy beneath, 

 oblong-lanceolate, pinnate ; divisions ovate, obtusely lobed ; indusium 

 obscure, consisting of a few jointed hairs.. 



20. ONOCLEA (including STRUTHIOPTERIS), SENSITIVE FERN. 

 (Name, from the Greek, meaning a closed vessel, referring to the berry- 

 like fructification.) 



O. sensibilis, Linn. Brake. Common in wet places, and often a 

 weed in hilly pastures ; sterile fronds of all sizes up to 2° high, broadly 

 triangular-ovate, the rhachis winged ; pinnae not many, lanceolate, entire, 

 or obtusely lobed less than half way to the midrib, veins everywhere re- 

 ticulated ; fertile fronds with few, closely appressed pinnae. 



O. Struthitfpteris, Hofim. Ostrich Fern. Alluvial grounds, N. ; 

 sterile fronds tall, 2°-5° high, lanceolate, narrowed at the base into a 

 short, angular stalk, pinnate ; pinnae very many, narrowly lanceolate, 

 pinnatifid more than half way to the midrib ; lobes numerous, oblong ; 

 fertile fronds very much shorter, blackish, standing erect after the others 

 have withered. 



21. DAVALLIA. (Named for M. Davall, a Swiss botanist.) Many 

 tropical or sub-tropical species, many cult, in conservatories. 



D. Canariensis, Smith. Hare's-foot Fern. Canary Islands, etc. ; 

 rootstock creeping above ground, covered with brownish scales, and 



