FiLiCES. (ferns.) 689 



§ 2. POL 1 STIC HUM. Indnsium orbicular and entire, peltate , Jixed 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. acrostichoides, Swartz. (Christmas Fern.) (PI. 19, fig. 3, 4.) 

 Frond lanceolate (l-:2^° higli), stalked; pinnce linear-lanceolate, somewhat 

 scythe-shaped, lialf-lialberd-shaped at the slightly stalked base, serrulate with 

 appressed bristly teeth ; the fertile (upper) contracted and smaller, beariug con- 

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

 surface. — Var. ixcIsum is a state witli cut-lobed pinnae, a not unfrequent case 

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

 woods, especially northward. July. 



11. A. Lonchitis, ^^wartz. 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 (T 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, acule^tum, Swartz, var. Braunii, Koch. Fronds spreading 

 (1^-2° long), oblong-lanceolate in outline, with a tapering base, the lower of 

 the many pairs of oblong-lanceolate pinna 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. CYSTdPTEEIS, 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-Tis, a bladder, and impis./ern, from the inflated indusium.) 



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

 (I -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 

 bstttle stalk wliich is fully as long), 2 -3-pinnate ; the pinnte and pinnules ovata 

 or lanceolate in outline, irrearularlv mnnatifid or cut-tootheA, mostly acute. 



