Selaginella hansenii
Selaginella densa
Hansen's spike-moss
compact selaginella, dense clubmoss, lesser spikemoss, prairie club-moss, Rocky Mountains spike-moss, small clubmoss
not readily fragmenting, prostrate, upperside and underside structurally different, irregularly forked, branches determinate, tips upturned.
decumbent or creeping, not readily fragmenting, irregularly forked, without budlike arrested branches, tips straight;
main stem upperside and underside structurally slightly different, conspicuously indeterminate, lateral branches radially symmetric, conspicuously or inconspicuously determinate, strongly ascending, 2–3-forked.
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).
essentially monomorphic, in poorly defined pseudowhorls of 5 or 6, tightly appressed, ascending, green, linear to linear-lanceolate, (2.7–)3–5 × 0.4–0.7 mm (upperside leaves smaller than underside ones, also smaller on ascending buds);
abaxial ridges present;
base long-decurrent, oblique, and glabrous on underside leaves, slightly decurrent, oblique, and sometimes pubescent on upperside leaves;
margins long-ciliate, cilia transparent, mostly ascending or spreading on proximal 1/2, ascending on distal 1/2, 0.07–0.17(–0.2) mm;
apex slightly keeled to plane, rather obtuse, abruptly long-bristled;
bristle white or transparent, puberulent, (1–)1.25–1.9 mm.
solitary, 5–7 mm;
sporophylls ovate-deltate to ovate-triangular, abaxial ridges not prominent, base glabrous, margins short-ciliate, apex bristled.
solitary, (0.5–)1–3(–4) cm;
sporophylls ovate-lanceolate, seldom ovate, abaxial ridges well defined, base glabrous, margins ciliate entire length or dentate near tip, apex usually long-bristled.
borne on upperside of stems, throughout stem length, 0.25–0.45 mm diam.
borne on upperside of stems, throughout stem length, 0.2–0.35 mm diam.
Selaginella hansenii
Selaginella densa
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.)
Selaginella densa has been treated as including three varieties: var. densa, var. scopulorum (Maxon) R. M. Tryon, and var. standleyi (Maxon) R. M. Tryon (R. M. Tryon 1955), which are recognized here at the species level. Intermediates between S. densa and the other two species of the group may represent ecological variations of the species, hybrids between species within the complex, or hybrids with other closely related species, such as S. watsonii. This group is in need of detailed systematic studies. Megasporangia with only two well-developed megaspores have been observed, which may indicate apogamy and the presence of different races as found in S. rupestris.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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