Selaginella hansenii
Selaginella ×neomexicana
Hansen's spike-moss
not readily fragmenting, prostrate, upperside and underside structurally different, irregularly forked, branches determinate, tips upturned.
radially symmetric, underground (rhizomatous) and aerial, not readily fragmenting, irregularly forked; rhizomatous and aerial stems often with 1 branch arrested, budlike, tips straight; rhizomatous stems sometimes difficult to distinguish, without obvious living budlike branches;
aerial stems erect to ascending, budlike branches mostly restricted to stem base (more conspicuous in ascending stems).
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).
dimorphic, not clearly ranked.
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 cm;
sporophylls ovate-lanceolate to lanceolate, abaxial ridges prominent, base glabrous, margins denticulate, apex keeled, short-bristled.
borne on upperside of stems, throughout stem length, 0.25–0.45 mm diam.
borne on upperside of stems, restricted to lower 1/2 on erect stems or throughout stem length on ascending stems, 0.2–0.3 mm diam.
stem leaves deciduous or persistent on base of emergent aerial stem, abruptly adnate, pubescent.
stem leaves appressed, ascending, green, linear-lanceolate, 1.9–2.7 × 0.36–0.46 mm;
abaxial ridges present;
base abruptly adnate, rounded, pubescent;
margins long-ciliate, cilia white, whitish to transparent or opaque, long and spreading at base, short to dentiform and ascending toward apex, 0.06–0.17 mm;
apex keeled;
bristle whitish to white, greenish to yellowish opaque, slightly puberulent, 0.3–0.46 mm.
Selaginella hansenii
Selaginella ×neomexicana
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 × neomexicana is treated here as a hybrid, following R. M. Tryon (1955). Plants of this hybrid lack megaspores and megasporangia and have misshapen microsporangia. Several hypotheses for its origin have been advanced. It is clearly allied to S. rupincola, with which it shares white, long, spreading, marginal cilia on the leaves, hairs sometimes running along the ridges of the abaxial groove of the leaf, obscure rhizomatous underground stems, and buds mostly restricted to the base of aerial stems. Tryon (1955) suggested that the two presumed parents were S. rupincola and S. mutica, because S. × neomexicana has been found growing with S. mutica (usually var. limitanea). The usually strongly keeled apex in S. × neomexicana is a feature of S. mutica, and the range of S. × neomexicana is within the range of the two presumed parents. Selaginella underwoodii might conceivably be the second parent instead; its range overlaps the ranges of the putative hybrid and S. rupincola. It is possible that S. × neomexicana may represent an asexual race of S. rupincola. More detailed studies are necessary to determine the reproductive biology and cytology of this presumed hybrid and to assess its relationships.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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