Cystopteris protrusa
Cystopteris tennesseensis
lowland bladderfern, lowland brittle fern, lowland fragile fern, southern bladder fern, southern fragile fern
Tennessee bladder fern
creeping, not cordlike, internodes long, 0.5–1 cm, with persistent petiole bases, covered with tan to golden hairs, especially toward apex;
scales tan to light brown, ovate-lanceolate to lanceolate, radial walls thin, luminae tan, mostly crowded at stem apex.
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.
seasonally dimorphic, clustered 1 to several cm beyond persistent old petiole bases, especially in late spring and early summer, to 45 cm, bearing sori (earliest leaves smaller, sterile, coarsely divided, margins with rounded teeth; subsequent leaves larger, fertile, more finely divided, margins with sharply pointed teeth).
monomorphic, crowded near stem apex, to 45 cm, nearly all bearing sori.
mostly green to straw-colored throughout, shorter than or nearly equaling 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, 1-pinnate-pinnatifid to 2-pinnate, widest at or just below middle, apex broadly acute;
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 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 serrate;
proximal pinnae pinnatifid to pinnate-pinnatifid, ± equilateral, basiscopic pinnules not enlarged, basal basiscopic pinnules 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.
mostly directed into teeth.
directed into teeth and notches.
ovate to cup-shaped, lacking gland-tipped hairs.
cup-shaped, apex truncate, with scattered, unicellular, gland-tipped hairs.
spiny, usually 28–34 µm. 2n = 84.
spiny, usually 38–42 µm. 2n = 168.
Cystopteris protrusa
Cystopteris tennesseensis
The terrestrial habit and characteristic stem features (golden hairs and protruding apex) readily distinguish Cystopteris protrusa from other Cystopteris species with which it may be sympatric (C. tenuis, C. tennesseensis, and C. bulbifera). Cystopteris tennesseensis and C. tenuis are allotetraploids that have C. protrusa as one parent. The other progenitor for C. tennesseensis is C. bulbifera, and a presumably extinct diploid is proposed here as the progenitor for C. tenuis. When C. protrusa is sympatric with either of these derived tetraploid species, sterile triploids are often produced. In addition, there are sterile autotriploids within C. protrusa (C. H. Haufler et al. 1985).
(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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