FILICES. (FERNS.) 597 



■crowded. Indusium flat, scarious, orbicular or round-kidney-shaped, covering 

 the sporangia, attached to the receptacle at the centre or at the sinus, opening 

 all round the margin. — Fronds mostly 1 -3-pinnatc. (Name do-rribiov, a small 

 shield, from the shape of the indusium.) 



§ 1. DRYOPTERIS, Adans., Schott. (NephrJdium, Rich, in part. Lastrea, 

 Bory.) — Indusium round-kidney -si taped, or orbicular vcitii a narrow sinus, fixed at 

 the sinus : fronds membranaceous or thlnnish. 



* Veins simple or simply forked and straight : fronds annual, decaying in autumn, 



the stalks and creeping rootstocks nearly naked. (Thclypteris, Schott.) 



1. A. Tlielj'pteris, Swartz. Frond pinnate, lanceolate in outline; the 

 slightly rcfiexed or horizontal pinnae gradually diminishing in length from near the 

 base to the ajxx, sessile, linear-lanceolate, deeply pinnatifid, with oblong nearly 

 entire obtuse lobes, or appearing acute from the strongly revolute margins in fruit; 

 veins mostly forked, bearing the crowded fruit-dots (soon confluent) near their mid- 

 dle. (Polypodium Thelyptcris, L.) — Marshes; common. Aug. — Stalk 1° 

 long or more, usually longer than the frond, which is of thicker texture than in 

 the next, slightly downy ; the fruit-dots soon confluent and covering the whole 

 contracted lower surface of the pinnas. (Eu.) 



2. A. Novefooracense, Willd. Frond pinnate, oblong-lanceolate in out- 

 line, tapering below, from the loiver pinnce (2 -several pairs) being gradually shorter 

 anddeflexed; the lobes flat, broadly oblong ; their veins aU simple except in the 

 lowest pairs, bearing scattered fruit-dots (never confluent) near the margin. (Poly- 

 podium Noveboracense, L. A. thelypteroides, Swartz.) — Swamps and moist 

 thickets; common. July. — Frond pale green, delicate and membranaceous, 

 nearly as the last, except in the points mentioned. 



* * Veins, at least the lowermost, more than once forked or somewhat pinnately branch- 

 ing ; the fruit-bearing velnlets often obscure or vanishing above the fruit-dot : fronds, 

 at least the sterile ones, often remaining green through the winter: stalks and apex 

 of the scaly thickened rootstocks chaffy, and often the main rhachls also when young. 



■*- Frond twice pinnate and with the pinnules pinnatifid or deeply incised: indu- 

 sium deciduous. 



3 A. SpitlUlOSUm, Swartz. Frond oblong or ovate-oblong in outline 

 (1° -2° long), lively green, smooth; pinnules oblong or oblong-linear, mostly 

 obtuse, horizontal, crowded, the lower deeply pinnatifid into linear-oblong obtuse 

 lobes which are sharply cut-toothed, the upper cut-pinnatifid or incised, with the 

 shorter lobes few-toothed at the apex ; margin of the indusium denticulate or 

 beset with minute stalked glands. (A. intermedium, Muhl. Dryoptcris inter- 

 media, erf. 1.) — Woods, everywhere common. July. — Exhibits a variety of 

 forms, some of them clearly the same as the European plant, more commonly 

 intermediate in appearance between it and 



Var. dilatatlini. Frond broader, ovate or triangular-ovate in outline ; 

 pinnules lance-oblong, the lower sometimes pinnately divided ; indusium smooth 

 and naked. (A. dilatatum, Willd.) — A dwarf state, fruiting when only 5' -8' 

 high, answers to var. (of Lastrsea dilatata) dumetorum. A peculiar form (A 

 campyloptcrum, Kunze? and Dryoptcris dilatata, chiefly, ed. 1) has the pinna;, 

 pinnules, and their divisions remarkably crowded, and directed obbquely forwards 



