FEEN FAMILY. 369 



midrib; divisions very numerons, nearly 1' long, somewhat scythe-shaped, 

 rather acute, serrate with incurved teeth ; fhiit-dots very near the midvein. 



A. erist^tum. Wet places in woods, common : fronds narrowly oblong, 

 l°-2° high, 3' -5' wide, rather rigid, erect; pinnae triangular-ovate, broadest 

 at base, pinnatifid almost to the midrib, divisions not many, oblong, obtuse, 

 finely serrate, the largest ones sometimes toothed or pinnatifid-lobed ; fruit-dots 

 half-way between midvein and margin. — Var. ClintoniInum, in swampy 

 woods, N., is very much larger every way, with fruit-dots nearer the midvein, 

 and is often mistaken for A. Goldianum. — Var. FloridAndm, in wet woods 

 S., has the lower pinnae triangular-lanceolate and sterile, but the upper ones 

 fertile, narrower and longer, with very short obtuse rather distant divisions, 

 which are.decurrent on the winged secondary rhachis. 



•1- t- Fronds imperfectly evergreen, twice or thrice pinnate : the divisions cat- 

 toothed or indsea: fruit-dots not near the margin : indusium rather small, 

 withering away. 



A. SpiuuldSUIU. Shady woods, very common N. : fronds thin, oblong- 

 ovate ; pinnae oblong-lanceolate, the lower ones broader and somewhat triangu- 

 lar ; pinnules very numerous, oblong-ovate, pinnately incised, the oblong lobes 

 with spinulose teeth toward the ends ; indusium smooth or minutely glandular 

 at the margin. — Has several forms. — Var. dilatXtum, in mountainous places, 

 N., is larger, broader in outline and commonly but twice pinnate ; pinnules of 

 the lowest pinnae greatly elongated. — Var. Bo6ttii, in swampy woods N., is 

 2° - 3° high, of narrow outline, barely twice pinnate, with oblong-ovate toothed 

 pinnules, or the lower ones pinnatifid : — it runs apparently into A. cristatum. 



•<-->-■»- Fronds fully eoergrern, thickish, about twice-pinnate : fruit-dots near the 

 margin ; indusium thickish, convex, persistent. 



A. margiudile. Eocky woods, common N. : fronds l°-2° long, ovate- 

 oblong, bluish-green, the stalk very chaffy ; pinnae lanceolate, 3' - 5' long ; 

 pinnules oblong, often curved, entire or obtusely toothed, attached by a broad 

 base to the narrowly winged secondary rhachis ; fruit>dots close to the margin, 

 rather large. 



§ 2. Poi/TSTiCHtTM. Indusium orbicular, peltate, attached by the centre to a 

 short stalk: veins forking, free : wild species of the country. 



A. acrosticholdes. Rocky woods, common; fronds I°- 2° high, grow- 

 ing in crowns, with chaify rootstooks and stalks, evergreen, shining, lanceolate, 

 simply pinnate ; pinnae numerous, -oblong-lanceolate from an unequal half- 

 halberd-shaped base, serrulate with bristle-pointed teeth, rarely incised, upper 

 ones of the fertile frond smaller and bearing copious soon confluent fruit-dots. 



§3. Ctkt6mium. Indusium as in § Poltstichum. Fronds once pinnate : 

 veins pinnate from the midrib, pinnately branching, the veinlefs reticulated 

 and forming arched meshes with 1-3 f-ee included veinlets rising from the 

 base of the arch : exotic. 



A. falcktvmi. Cult, from Japan: fronds l°-20high, 5' -9' broad; base 

 of stalk chaffy with large scales ; pinnae thick and shining, end one large and 

 rhomboid or halberd-shaped ; side ones few or many, oblong-ovate, long-pointed, 

 nearly entire, lower side of base roimded, upper side angled or slightly auricled ; 

 fruit-dots in many rows on all or nearly all the pinnee. 



16. CYSTOPTBRIS. (Greek for Bladder Fern, alluding to the thin, 

 sometimes inflated indusium.) Species few, mostly Northern. 



C. flr^gilis. Shaded or moist rocky places, common N. : fronds very deli- 

 cate, 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. btllbifera. Wet places, oftenest in ravines, from N. Carolina N. : 

 fronds l°-3° liigh, 3' -5' wide at the base, narrowed above and much elon- 

 gated, twice pinnate, bearing scattered bulblets beneath ; pinnules oblong, ob- 

 tuse, toothed or pinnatifid ; indusium roundish, truncate on the upper side. 

 24 



