FILICES. (FERNS.) 597 



crowded. Indusium flat, scarious, orbicular or round-kidnev-shuped, covering 

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

 all round the margin. Fronds mostly 1 -3-pinnate. (Name donridiov, a small 

 shield, from the shape of the indusium.) 



1. DRY6PTERIS, Adans., Schott. (Nephrodium, Rich, in part. Lastrea, 

 Bory.} Indusium round-kidney-shaped, or orbicular with a narrow sinus, fixed at 

 the sinus : fronds membranaceous or thinnish. 



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



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



1. A. TlielypteriS, Swartz. Frond pinnate, lanceolate in outline; the 

 slightly reflexed or horizontal pinnce gradually diminishing in length from near the 

 base to the apex, 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. (Polypoclium Thelypteris, 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 pinnse. (Eu.) 



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

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

 and defiexed ; the lobes flat, broadly oblong ; their veins all 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 veinlets 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 rhachis also when young, 



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

 sium deciduous. 



3. A. Spinillosillll, 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 arc 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. Dryopteris inter- 

 media, ed. 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. <lilat;\tlllll. 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. 

 cainpylopterum, Kniw? and Dryopteris dilatata, Chiefly, <r/. 1) has tliv pinna, 

 pinnules, and their divisions remarkably crowded, and directed obliquely fonvai <la 



