FILICES. (FERNS.) 689 



2. POLYSTICHUM. Indusium orbicular and entire, peltate, fixed by the 

 depressed centre ; fronds rigid and coriaceous, evergreen, very chaffy on the 

 rhachis, etc. ; pinnce or pinnules auricled at base on the upper side, crowded, 

 the teeth or lobes bristle-tipped. 



# Fronds simply pinnate. 



10. A. acrostichoid.es, Swartz. (CHRISTMAS FERN.) (PI. 19, fig. 3,4.) 

 Frond lanceolate (l-2- high), stalked; pinnce linear-lanceolate, somewhat 

 scythe-shaped, half-halberd-shaped at the slightly stalked base, serrulate with 

 apprised bristly teeth ; the fertile (upper) contracted and smaller, bearing con- 

 tiguous fruit-dots near the midrib, which are confluent with age, covering the 

 surface. Var. iNcisuM is a state with cut-lobed pinnae, a not unfrequent case 

 in the sterile fronds ; sometimes with all the tips fertile. Common in rocky 

 woods, especially northward. July. 



11. A. Lonchitis, Swartz. Frond linear-lanceolate (9 - 20' high), scarcely 

 stalked, very rigid ; pinnce, broadly lanceolate-scythe-shaped, or the lowest trian- 

 gular, strongly auricled on the upper side, and wedge-truncate on the lower, 

 densely spinulose-toothed (!' or less in length), copiously fruit-bearing; fruit- 

 dots contiguous and near the margins. Woods, southern shore of Lake Su- 

 perior, and northward. (Eu.) 



* * Fronds bipinnate. 



12. A. aculeatum, Swartz, var. Braunii, Koch. Fronds spreading 

 (li-2 long), oblong-lanceolate in outline, with a tapering base, the lower of 

 the many pairs of oblong-lanceolate pinnae gradually reduced in size and ob- 

 tuse ; pinnules ovate or oblong, obtuse, truncate and almost rectangular at 

 base, short-stalked, or the upper confluent, sharply toothed, beset with long 

 and soft as well as chaffy hairs. Deep woods, mountains of New Eng., N. Y., 

 and Penn., and northward. (Eu.) 



14. CYSTOPTERIS, Bernhardi. BLADDER FERN. (PI. 19.) 



Fruit-dots roundish, borne on the back of a straight fork of the free veins ; 

 the delicate indusium hood-like or arched, attached by a broad base on the in- 

 ner side (toward the midrib) partly under the fruit-dot, early opening free at 

 the other side, which looks toward the apex of the lobe, and is somewhat 

 jagged, soon thrown back or withering away. Tufted ferns with slender 

 and delicate 2 - 3-pinnate fronds ; the lobes cut-toothed. (Name composed of 

 Kva-Tts, a bladder, and TTT* pis, fern, from the inflated indusium.) 



1. C. bulblfera, Bernh. (PI. 19, fig. 1-3.) Frond lanceolate, elongated 

 (1-2 long), 2-pinnate; the pinnae lanceolate-oblong, pointed, horizontal (1 - 

 2' long); the rhachis and pinnce often bearing bulblets underneath, wingless; 

 pinnules crowded, oblong, obtuse, toothed or pinnatifid ; indusium short, trun- 

 cate on the free side. Shaded ravines, not rare from N. Eng. to Ark., com- 

 moner on calcareous rocks. July. Specimens from Tenn. and Ark. have 

 sometimes shorter fronds and few or no bulblets, indicating an approach to the 

 next species. 



2. C. fragilis, Bernh. Frond oblong-lanceolate (4-8' long, besides the 

 biittle stalk which is fully as long), 2 -3-pinnate ; the pinnae and pinnules ovate 

 or lanceolate in outline, irregularly t>innatifid or cut-toothed, mostly acute. 



