Selaginella apoda
Selaginellaceae
meadow spike-moss, sélaginelle apode
spike-moss family
prostrate to short-creeping, sparsely branched, branches mostly simple or 1-forked, flat, not articulate, glabrous.
leafy, branching dichotomously, regularly or irregularly forked or branched, protostelic (sometimes with many protosteles or meristeles), siphonostelic, or actino-plectostelic.
delicate, papery.
on 1 plant dimorphic or monomorphic, small, with adaxial ligule near base, single-veined [rarely veins forked].
paired or solitary, lax, flattened, 1–2 cm;
sporophylls ovate to ovate-deltate, strongly keeled, keel dentate, base slightly cordate to rounded, margins with scattered teeth, apex acuminate;
megasporophylls larger and wider than microsporophylls, usually on underside of strobili.
(clusters of overlapping sporophylls) sometimes ill-defined, terminal [lateral], cylindric, quadrangular, or flattened.
short-stalked, solitary in axil of sporophylls, opening by distal slits.
of 2 types (plants heterosporous), megaspores (1–2–)4, large, microspores numerous (hundreds), minute.
(fertile leaves) monomorphic or adjacently different, slightly or highly differentiated from vegetative (sterile) leaves.
axillary, throughout stem length or restricted to proximal 1/3 of stem, 0.05–0.1 mm diam.
(modified leafless shoots producing roots) present or absent, geotropic, borne on stems at branch forks, throughout, or confined to base of stems.
leaves distant, green, ovate to ovate-lanceolate, 1.35–2.25 × 0.75–1.35 mm;
base slightly cordate;
margins green or with 1 row of transparent cells, serrate;
apex acute, ending in teeth.
leaves ovate-lanceolate, 1–1.6 × 0.45–0.7 mm;
base oblique on inner side, rounded and prominent on outer side;
margins green or with row of transparent cells, serrate;
apex straight, acuminate to long-acuminate.
Selaginella apoda
Selaginellaceae
Selaginella apoda is the central component of a taxonomically difficult species complex of eastern North America. It is closely related to S. eclipes (see discussion) and S. ludoviciana. Naturally occurring and experimental hybrids between S. apoda and S. ludoviciana have been reported (P. Somers and W. R. Buck 1975; T. R. Webster 1990). Also, some evidence indicates that hybrids may occur between S. apoda and S. eclipes. More studies are needed in this complex.
The species in the S. apoda complex may be best classified under subg. Homostachys of J. G. Baker (1883, 1887), with which they share flattened strobili and larger sporophylls (megasporophylls) that are usually in the same plane as the vegetative lateral leaves. They are, however, treated here with the other heterophyllous species of subg. Stachygynandrum until a reassessment of the classification of the genus Selaginella can be made.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Selaginellaceae traditionally include only one genus of living plants, Selaginella (A. C. Jermy 1990b; R. M. Tryon and A. F. Tryon 1982). Some authors (O. Kuntze 1891–1898, vol. 2, pp. 824–827; W. Rothmaler 1944), however, have segregated other genera based on generic concepts established by A. Palisot de Beauvois (1805, pp. 95–114), who recognized four genera. A. F. Spring (1850) combined the four genera into the broadly defined genus Selaginella. Spring's generic delimitation has resulted in misinterpretations that created many nomenclatural problems and partly led to the continued recognition of only one genus. Nevertheless, species in Selaginella fall into at least three well-defined groups, all present in North America, that may be recognized as genera based on anatomy, embryology, morphology and arrangement of the leaves and sporophylls, and morphology and symmetry of the strobilus. North American Selaginellaceae, which represent only a small portion of the family, are treated here in Selaginella, pending a full revision of the family worldwide.
Species in the fossil genus Selaginellites Zeller, which dates to the Carboniferous period, presumably are congeneric with Selaginella. Among the fern allies, Selaginellaceae are related only distantly to the other lycopod families, Lycopodiaceae and Isoëtaceae (R. M. Tryon and A. F. Tryon 1982).
Genera 1, over 700 species (38 species in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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