Cystopteris Bernh.

Filicule (fr)

Genus

Pteridophytes > Polypodiales > Cystopteridaceae

Characteristics

Petiole slender, with 2 bundles, scaly only at the base, much shorter than the blade in our spp.; blade mostly 2–4 times pinnate or ternate-pinnate; veins forking, free, reaching the margin, slightly thickened at the tip; sori rotund, each borne on a veinlet that continues to the margin; indusium hyaline, basiscopic (i.e., attached under the proximal margin of the sorus on the entering veinlet), ± hood-like, its free tip arched over the sorus (towards the distal margin of the pinnule) and commonly thrown back as the sorus expands, sometimes tiny and caducous; delicate woodland ferns with deciduous lvs, the petiole-bases not persistent. 10, cosmop.Our spp. of Cystopteris enter into a polyploid complex that compromises the essential differences among the species. C. bulbifera and C. protrusa are diploid, 2n=84. C. fragilis is tetraploid (2n=168) in our area, but is considered to include some hexaploids and octoploids in the Old World. Two other established polyploids combine the features of C. bulbifera with those of C. protrusa (in one case) or C. fragilis (in the other). C. tennesseensis Shaver (tetraploid) may be an alloploid derived from C. bulbifera and C. protrusa, and C. laurentiana (Weath.) Blasdell may be an alloploid derived from C. bulbifera and C. fragilis var. fragilis. Both of these apparent alloploids usually have some poorly developed or abortive bulbils along the lf-rachis, and they tend to have some minute glands on the indusia. In C. tennesseensis the blade is widest at the base, as in C. bulbifera, whereas in C. laurentiana it is widest above the base, as in C. fragilis. C. laurentiana is northern, occurring from Nf. and Que. to Wis. and n. Minn., with a disjunct station in Centre Co., Pa. C. tennesseensis is more southern, occurring from Va. and Ky. to Kans. and Okla. There are also some ± sterile polyploids in this complex. C. ×illinoensis R. C. Moran (triploid, 2n=126) may reflect hybridization of C. bulbifera with C. fragilis var. mackayi, and C. ×wagneri R. C. Moran (tetraploid, 2n=168) may reflect hybridization of C. tennesseensis with C. fragilis var. mackayi.
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Plants small, summer-green. Rhizomes long or shortly creeping, blackish brown, glabrate or densely red-brown pubescent, sparsely scaly; scales brown or brownish, thin, ovate to broadly lanceolate. Fronds distant, approximate, or caespitose, thin; stipe dark brown at base, upper part stramineous or chestnut-colored; lamina 2-or 3-pinnate, rarely 4-pinnate or more divided, ovate-lanceolate, ovate-triangular, or subpentagonal; pinnae with anadromous pinnules, shortly stalked, unequally sided or subequilateral at base; minutely toothed at segment margin; veins free, forked or pinnate, terminating in teeth or emarginations. Lamina thinly herbaceous or herbaceous, green when dried, stipe, rachis, costae, and costules with few small scales at base, and multicellular hairs or unicellular glandular hairs, lamina usually glabrate. Sori orbicular, abaxial on veins, sorophore slightly protuberant, annulus of sporangium consisting of 14-16 cells; indusia ovate, lanceolate, orbicular, or shallowly cup-shaped, attached at proximal side of sorophore, membranous, persistent, covering sporangia when young, hidden at maturity. Spores bilateral, dark brown, bean-shaped, perispore usually with spines, rarely with folds. x = 42.
Terrestrial ferns. Rhizomes slender, blackish, decumbent or creeping, scaly. Fronds 2-3-pinnate, sparsely scaly, delicate, often dying down in winter; veins free. Sori round, borne on veins. Indusia ovate or hood-like, attached across the veins on basiscopic side of sori, arching over the sporangia. Spores monolete.
Small delicate ferns. Rhizome short-creeping, scaly; scales brown, hair-tipped. Fronds crowded at rhizome apex. Stipe slender, grooved, scaly at the base. Lamina 1-2-pinnate, delicate, brittle; veins free. Sori rounded; indusium delicate, pale, attached only at the inflated base, marcescent.
Sori globose; indusium delicate, attached at base, elsewhere free. Sporangia globose, without paraphyses; spores reniform, smooth to muriculate. Rhizome short, clad in brown broad attenuate paleae. Lamina thin, flaccid, pinnate to bipinnate; veins free. A few spp. of uncertain delimitation.
Sori not elongate along veins
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Hardiness (USDA) 4-9

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