664 FILICES. (FERNS.) 



12. ASPIDIUM, Swartz. SHIELD-FERN. WOOD-FERN. (PI. 18.) 



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

 sium 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, 

 j a small shield, from the shape of the indusiuin.) 



1. DRY6PTERIS, Adanson. (Nephrodium, 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- 

 nae horizontal or slightly recurved, linear-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 ; intlusium 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. Noveborac^nse, Swartz. Fronds pinnate, lanceolate in outline, 

 tapering both ways from the middle ; pinnae 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- 

 ebbracense, L. A. thelypteroides, 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, often remaining green through the winter : 

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

 rhachis also. 

 - Fronds small, pinnate : pinnae 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" t 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. Falls of 

 the St. Croix, Wisconsin, Dr. Parry ; Wisconsin River, Lapham, Berlin Falls, 

 N. Hampshire, H. Willey, Mt. Kineo, Maine, C. E. Smith, and northward. 

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

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



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



4. A. Spinul6sum, Swartz. Stipes with a few pal e-brotvn deciduous scales; 

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



