664 FILICES. (ferns.) 



12. ASPIDITJM, Swartz. Shield-Fekn. Wood-Fern. (PI. 18.) 



Fruit-dots round, borne on the back or rarely at the apex of the veins. Indu- 

 siura covering the sporangia, flat or flattish, scarious, orbicular and peltate at 

 the centre, or round-kidney-shaped and fixed either centrally or by the sinus, 

 opening all round the margin. Stipe continuous (not articulated) with the 

 rootstock. — Our species have free veins, and 1-3-pinnate fronds. (Name, 

 do-rridtov, a small shield, from the shape of the indusium.) 



§1. DRYOPTERIS, Adanson. (Nephrbdium, Rich., in part, Hook. Lastrea, 

 Bory. ) Indusium round-kidney-shaped, or orbicular with a narrow sinus. 



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



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



1. A. Thelypteris, Swartz. Fronds pinnate, lanceolate in outline ; pin- 

 nee horizontal or slightly recurved, lineai'-lanceolate, deeply pinnatifid, the lowest 

 pairs scarcely smaller ; lobes oblong, entire, obtuse or appearing acute when in 

 fruit from the strongly revolute margins; veins mostly forked, bearing the (soon 

 confluent) fruit-dots near their middle; indusium minute, smooth and naked. 

 (Polypodium Thelypteris, L.) — Marshes: common. Aug. — Stalk 1° long 

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

 next, and slightly downy. (Eu.) 



2. A. Noveboracense, Swartz. Fronds pinnate, lanceolate in outline, 

 tapering both ways from the middle ; pinna? lanceolate, the lowest 2 or more pairs 

 gradually shorter and deflexed ; lobes flat, oblong, basal ones often enlarged and 

 incised ; veins simple, or forked in the basal lobes ; fruit-dots distinct, near the 

 margin; indusium minute, the margin glanduliferous. (Polypodium Nov- 

 eboracense, L. A. thel ypteroides, Swartz. ) — Swamps and moist thickets : 

 common. July. — Frond pale-green, delicate and membranaceous, hairy be- 

 neath along the midribs and veins. 



* * Veins, at least the lowest ones, more than once forked or somewhat pinnately 



branching ; the fruit-bearing veinlets often obscure or vanishing above the fruit- 

 dot : fronds, at least the sterile ones, ojlen remaining green through the winter: 

 stalks and apex of the thickened rootstock scaly or chaffy, and often the main 

 rhachis also. 

 •*- Fronds small, pinnate: pinna pinnatifid: indusia very large, persistent. 



3. A. fragrans, Swartz. Fronds (4' -12' high) glandular and aromatic, 

 narrowly lanceolate, with linear-oblong pinnately-parted pinna? ; their crowded 

 divisions (2" long) oblong, obtuse, toothed or nearly entire, nearly covered be- 

 neath with the very large thin imbricated indusia, which are orbicular with a 

 narrow sinus, the margin sparingly glanduliferous and often ragged. — Shaded 

 trap-rocks, Falls of the St. Croix, Wisconsin, Dr. Parry ; Wisconsin River, 

 Lapham, Lake Superior, Canada, and high northward. — Rootstock stout, nearly 

 erect, densely chaffy, as are the crowded stipes and rhachis. 



-4- -t- Large (l°-2j° high), the fronds mostly twice pinnate with variously toothed 

 and incised pinnides : indusia rather small, shrivelled in age, or deciduous. 



4. A. spin.ul6sum, Swartz. Stipes with a few pale-brown deciduous scales ; 

 frond ovate-lanceolate, twice pinnate ; pinna: oblique to the rhachis, elongated-trian- 



