Delicate rock ferns with slender stipes, 2-4-pinnate blades, and roundish sori borne on the backs of the veins. Indusium membranous, hood-like, attached by a broad base on its inner side and partly under the sorus, early thrust back by the expanding sporanges and at least partly concealed by them, withering, the sori thus appearing naked with age. Veins free.

About 10 species mainly natives of temperate regions; the following in North America. Type species: Polypodium bulbiferum L.

1. Filix Bulbifera (L.) Underw. Bulblet Cvstopteris

Fig. 30

Polypodium bulbiferum L. Sp. PI. 1091. 1753. Cystopteris bulbifera Bernh. Schrad. Neues Journ. Bot.

12: 26. 1806. Filix bulbifera Underw. Nat. Ferns, ed. 6, 119. 1900.

Rootstock short, somewhat chaffy at the apex. Stipes clustered, 4'-6' long, light-colored; blades 1°-2 1/2° long, usually 3-pinnatifid, deltoid-lanceolate, the gradually tapering narrow apex sometimes greatly elongate; pinnae numerous, oblong-ovate to lanceolate-oblong, horizontal, pinnate; pinnules close or somewhat apart, unequally oblong-ovate, obtuse, at least the largest deeply pinnatifid and free, the others more or less adnate and variously incised; rachis and pinnae underneath bearing large fleshy bulblets, these falling and giving rise to new plants; indusia short, convex, truncate.

On wet rocks and in ravines, especially on limestone, Newfoundland to Manitoba, Wisconsin and Iowa, south to northern Georgia, Alabama and Arkansas. Ascends to 3500 ft. in Virginia. July-Aug.

2. Filix Fragilis (L.) Underw. Brittle Fern

Fig. 31

Polypodium fragile L. Sp. PI. 1091. 1753. Cystopteris fragilis Bernh. Schrad. Neues Journ.

Bot. 12: 27. 1806. Filix fragilis Underw. Nat. Ferns, ed. 6, 119. 1900.

Rootstock extensively creeping, chaffy, especially at the apex. Stipes 4'-10' long, slender, brittle; blades thin, broadly lanceolate, slightly tapering below, 4-10' long, 2-3-pinnatifid or pinnate; pinnae deltoid-lanceolate to deltoid-ovate, acute, deeply pinnatifid or pinnate, the segments ovate or oblong-ovate, pinnatifid or incised, acutish, mostly decurrent upon the usually winged rachis; indusia roundish or nearly ovate, deeply convex, delicate.

On rocks and in moist grassy woods, Newfoundland and Labrador to Alaska, south to Georgia, Alabama, Kansas, Arizona, and southern California. Also in Greenland. Almost cosmopolitan in distribution and very variable. Ascends to 5000 ft. in New Hampshire. May-July. Called also Bottle-, Brittle-, or Bladder-fern.

3. Filix Montana (Lam.) Underw. Mountain Cystopteris

Fig. 32

Polypodium montamim Lam. Fl. Franc. 1: 23.

1778. Cystopteris montana Bernh.; Desv. Mem. Soc.

Linn. Paris 6: 264. 1827. Filix montana Underw. Nat. Ferns, ed. 6, 119.

1900.

Rootstock slender, widely creeping, the leaves few and distant. Stipes 6'-9' long, slender; blades broadly deltoid-ovate, 3-4-pin-nate, about 4'-6' long and broad, the basal pinnae much the largest, unequally deltoid-ovate, their inferior pinnules 1'-2' long; pinnules deeply divided into oblong or ovate-oblong lobes, these deeply toothed or again pinnate; sori numerous; indusia ovate, deeply convex, delicate, very early thrust back and concealed or evanescent.

On rocks, Labrador and Quebec to British Columbia and Alaska, south to the northern shore of Lake Superior. Also in Colorado, and in northern Europe and Asia. . Aug. Called also Wilson's-. Mountain-, or Bladder-fern.