Selaginella hansenii
Selaginellaceae
Hansen's spike-moss
spike-moss family
not readily fragmenting, prostrate, upperside and underside structurally different, irregularly forked, branches determinate, tips upturned.
leafy, branching dichotomously, regularly or irregularly forked or branched, protostelic (sometimes with many protosteles or meristeles), siphonostelic, or actino-plectostelic.
with underside leaves slightly longer and narrower than upperside leaves, otherwise monomorphic, not clearly ranked, tightly appressed, ascending, green or green with red spots, or reddish, linear-lanceolate (underside) to linear-triangular (upperside), (2–)3–4.5 × 0.5–0.6 mm;
abaxial ridges present;
base abruptly adnate, pubescent (sometimes glabrous);
margins ciliate, cilia white to white opaque, strongly appressed and ascending, 0.03–0.1 mm;
apex with bristle white to white-opaque, 0.5–1.4 mm (those on underside leaves sometimes 1/4–1/2 longer than those on upperside leaves).
on 1 plant dimorphic or monomorphic, small, with adaxial ligule near base, single-veined [rarely veins forked].
solitary, 5–7 mm;
sporophylls ovate-deltate to ovate-triangular, abaxial ridges not prominent, base glabrous, margins short-ciliate, apex bristled.
(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.
borne on upperside of stems, throughout stem length, 0.25–0.45 mm diam.
(modified leafless shoots producing roots) present or absent, geotropic, borne on stems at branch forks, throughout, or confined to base of stems.
Selaginella hansenii
Selaginellaceae
Leaf dimorphism in Selaginella hansenii is only slightly and inconsistently expressed; the upperside leaves tend to be more lanceolate, short, and slightly thick, whereas the underside leaves tend to be more linear, longer, and thinner, but in some specimens the leaves are monomorphic. Red leaves are rare within Selaginella subg. Tetragonostachys, otherwise found in the flora only occasionally in S. rupestris. Such leaves are more common in S. steyermarkii Alston from southern Mexico and Guatemala and S. sartorii Hieronymus from Mexico.
(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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