PERN FAMILY. 369 



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

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



A. crist^tum. Wet places in woods, common ; fronds narrowly oblong, 

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

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

 finely serrate, the largest ones sometimes toothed or pinnatiiid-lobed ; fruitdots 

 half-way between midvein and mai-gin. — Var. ClintoniXnum, in swampy 

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

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

 S., has the lower pinnse 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. 



■t- -H- Fronds imperfictly evergreen, twice or thrice pinnate : the divisions .cut- 

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

 withering away. 



A. Spmul6suin. Shady wodds, very common N. : fronds thin, oblong- 

 ovate ; pinnse 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. dilatA.tum, in mountainous places, 

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

 the lowest pinnas 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. 



I- -I- -I- Fronds fully evergreen, thicJcish, about twice-pinnate ; fruit-dots mar the. 

 margin : indusium thickish, convex, persistent. 



A. margin&le. Rocky woods, common N. ; fronds l°-2° long, ovate- 

 oblong, bluish-green, the stalk very chaffy ; piunas 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. PoLYSTiciiUM. 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 1° -2° high, grow- 

 ing in crowns, with chaffy rootstocks and stalks, evergreen, shining, lanceolate, 

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

 halberd-shapedbase, serrulate with bristle-pointed teeth, rarely incised, upper 

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



§3. Ctrt6m;ium. Indusium as in § Poltstichum. Fronds once pinnate : 

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

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

 baseof the arch: exotic. 



A. falektum. Cult, from Japan: fronds 1°- 2° high, 5' -9' broad; base 

 of st^lk chaffy with large scales ; pinnse 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 rounded, upper side angled or slightly auricled ; 

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



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

 sometimes inflated indusium.) Species few, mostly Northern. 



C. fr4gilis. Shaded or moist rocky places, common KT. : fronds very deli- 

 cate, 4' -8' long, with slender stalks, oblong-ovate, twice-pinnate; pinna; with 

 a narrowly margined rhachis ; pinnules oblong or ovate, toothed or incised, very 

 variable ; indusium pointed at the upper end. 



C. taulblfera. Wet places, oftenest in ravines, from N. Carolina N. : 

 fronds l°-3° high, 2' -5' wide at the base, narrowed above and much elon- 

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

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



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