Cystopteris reevesiana
Cystopteris tennesseensis
Reeves' bladderfern, Southwestern brittle fern
Tennessee bladder fern
creeping, not cordlike, internodes usually long, with scattered persistent petiole bases, hairs absent;
scales tan to brown, ovate to lanceolate, radial walls thin, luminae tan.
creeping, not cordlike, internodes short, heavily beset with old petiole bases, hairs absent;
scales usually tan to light brown, lanceolate, radial walls tan to brown, thin, luminae tan.
monomorphic, clustered at stem apex, to 45 cm, bearing sori throughout year.
monomorphic, crowded near stem apex, to 45 cm, nearly all bearing sori.
highly variable in color, from uniformly dark purple to uniformly straw-colored, but mostly dark purple at base, grading to straw-colored at junction with blade, shorter than blade, base sparsely scaly.
variable in color but mostly dark brown at base, gradually becoming straw-colored distally, shorter than blade, sparsely scaly at base.
ovate to elliptic, 2–3-pinnate, widest at or just below middle, apex short-attenuate;
rachis and costae lacking gland-tipped hairs or bulblets;
axils of pinnae with occasional multicellular, gland-tipped hairs.
deltate to narrowly deltate, 2-pinnate-pinnatifid, usually widest at or near base, apex short-attenuate;
rachis and costae with occasional unicellular, gland-tipped hairs, with or without bulblets (usually misshapen);
axils of pinnae with infrequent multicellular, gland-tipped hairs.
usually perpendicular to rachis, not curving toward blade apex, margins dentate to crenate;
proximal pinnae pinnate-pinnatifid to 2-pinnate, ± equilateral, basiscopic pinnules not enlarged;
basal basiscopic pinnules mostly short-stalked, base truncate to obtuse, distal pinnae deltate to ovate.
usually 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 to short-stalked, base truncate to obtuse;
distal pinnae ovate to oblong.
directed into teeth and notches.
directed into teeth and notches.
cup-shaped to lanceolate, gland-tipped hairs absent.
cup-shaped, apex truncate, with scattered, unicellular, gland-tipped hairs.
spiny, usually averaging 33–41 µm. 2n = 84.
spiny, usually 38–42 µm. 2n = 168.
Cystopteris reevesiana
Cystopteris tennesseensis
The finely dissected leaves, dark petioles, creeping stems, smaller spores, and terrestrial habit distinguish Cystopteris reevesiana from C. fragilis in the southwest. On rock and at high elevations, however, C. reevesiana can have stems with short internodes and leaves that are reduced in size and dissection (resembling C. fragilis). In southern Colorado, the two species are sympatric in some areas and form triploid hybrids. Cystopteris reevesiana and C. bulbifera are the diploid progenitors of C. utahensis, which occasionally crosses with C. reevesiana to produce sterile triploid hybrids of intermediate morphology.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Cystopteris tennesseensis, an allotetraploid species, has C. bulbifera and C. protrusa as diploid progenitors. The relative distinctiveness of these diploids suggests that identification of C. tennesseensis individuals should be straightforward. As with other members of Cystopteris, however, a series of features makes reliable recognition of this tetraploid challenging. For some characteristics (occasional unicellular, gland-tipped hairs and bulblets; short-attenuate, narrowly deltate blades), it is intermediate between its parents; for others (very short internodes and crowded leaves; occurrence on rock), it tends toward C. bulbifera. This unequal intermediacy, the multiple origins from genetically different individuals (C. H. Haufler et al. 1990), and the occurrence of sterile backcross triploids with its diploid progenitors in zones of sympatry has blurred the already subtle features distinguishing this allopolyploid. For example, some individuals of C. bulbifera may have very few glandular hairs, and some C. tennesseensis appear to lack glandular hairs entirely (R. F. Blasdell 1963). Further, sterile tetraploid hybrids (called C. × wagneri R. C. Moran) between C. tennesseensis and C. tenuis have been reported (R. C. Moran 1983) and verified through isozyme analyses (C. H. Haufler, unpubl. data). Finally, as discussed above, the recently recognized C. utahensis (C. H. Haufler and M. D. Windham 1991) is extremely similar morphologically to C. tennesseensis.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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