Cystopteris tenuis
Cystopteris utahensis
cystoptère ténue, Mackay's brittle fern, Mackay's fragile fern, upland brittle bladderfern
Utah bladderfern
creeping, not cordlike, internodes short, beset with old petiole bases, hairs absent;
scales tan to light brown, lanceolate, radial walls thin, luminae tan.
creeping, not cordlike, internodes short, heavily beset with old petiole bases, hairs absent;
scales lanceolate, ± clathrate, radial walls dark brown, thick, luminae clear.
monomorphic, clustered at stem apex, to 40 cm, nearly all bearing sori.
monomorphic, clustered at stem apex, to 45 cm, nearly all bearing sori.
dark at base, mostly green to straw-colored distally, shorter than or nearly equaling blade, base sparsely scaly.
green to straw-colored throughout or darker near base, shorter than blade, base sparsely scaly.
lanceolate to narrowly elliptic, 1(–2)-pinnate-pinnatifid, widest at or just below middle, apex short-attenuate;
rachis and costae lacking gland-tipped hairs or bulblets;
axils of pinnae lacking multicellular, gland-tipped hairs.
deltate to narrowly deltate, 2-pinnate-pinnatifid, usually widest at or near base, apex short-attenuate;
rachis and costae with unicellular, gland-tipped hairs, misshapen bulblets present or absent;
axils of pinnae usually with multicellular, gland-tipped hairs.
typically at acute angle to rachis, often curving toward blade apex, margins crenulate;
proximal pinnae pinnatifid to pinnate-pinnatifid, ± equilateral, basiscopic pinnules not enlarged;
basal basiscopic pinnules sessile, base cuneate to obtuse, distal pinnae ovate to narrowly elliptic.
typically perpendicular to rachis, not curving toward blade apex, margins serrate;
proximal pinnae pinnatifid to pinnate-pinnatifid, ± equilateral, basiscopic pinnules not enlarged;
basal basiscopic pinnules sessile or short-stalked, base truncate to obtuse, distal pinnae ovate to oblong.
directed into teeth and notches.
directed into teeth and notches.
ovate to cup-shaped, without gland-tipped hairs.
cup-shaped, apex truncate, with scattered, unicellular, gland-tipped hairs.
spiny, usually 39–50 µm. 2n = 168.
spiny, usually 39–48 µm. 2n = 168.
Cystopteris tenuis
Cystopteris utahensis
Long recognized as Cystopteris fragilis var. mackayi, C. tenuis was returned to species status by R. C. Moran (1983b). It is probably an allotetraploid originating from C. protrusa and an extinct diploid related to C. fragilis (C. H. Haufler 1985; C. H. Haufler and M. D. Windham 1991).
Cystopteris tenuis is common in eastern North America and less frequent at the northern and western perimeter of its range. In the center of its distribution (Minnesota, Iowa, Illinois, Wisconsin, Indiana, Ohio, Pennsylvania), the narrow, elliptic pinnae angled toward the blade apex and the rounded teeth make C. tenuis relatively distinct from C. fragilis and C. protrusa (although the early season, sterile leaves of C. protrusa often resemble those of C. tenuis). In the west and especially in the northeast, C. tenuis and C. fragilis are difficult to distinguish. For the most part, C. fragilis is confined to higher latitudes and elevations than C. tenuis, but the two species can be sympatric and occasionally form sterile tetraploid hybrids. Cystopteris protrusa and C. tenuis are infrequently sympatric, but where they are, sterile triploid hybrids can occur. Hybrids between C. tenuis and C. tennesseensis are recognized as C. × wagneri (R. C. Moran 1983). Hybridization between C. tenuis and C. bulbifera has also been reported (R. C. Moran 1982b). This hybrid, C. × illinoensis R. C. Moran, is known only from the type and needs to be studied further.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Cystopteris utahensis is an allopolyploid derived from the diploid species C. bulbifera and C. reevesiana (C. H. Haufler and M. D. Windham 1991). Because C. utahensis shares one parent (C. bulbifera) with C. tennesseensis and because of morphologic similarities between C. reevesiana and C. protrusa (the second diploid parent of C. tennesseensis), populations of C. utahensis were previously considered to have originated by long-distance dispersal from eastern populations of C. tennesseensis. Genetic studies using isozyme markers, however, indicated that C. utahensis was a distinct species and stimulated the discovery of morphologic criteria for distinguishing it from its eastern cousin. When combined with the geographic separation of the two tetraploids, the minor differences in indument features provide a means of circumscribing this genetically distinct species. Potential confusion in identifying C. utahensis arises because sterile triploid hybrids may form when it is sympatric with the more common diploid C. reevesiana.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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