Selaginella apoda
Selaginella sibirica
meadow spike-moss, sélaginelle apode
northern selaginella, Siberian spike-moss
prostrate to short-creeping, sparsely branched, branches mostly simple or 1-forked, flat, not articulate, glabrous.
radially symmetric, creeping or decumbent, not readily fragmenting, irregularly forked, without budlike arrested branches, tips straight;
main stem indeterminate, lateral branches conspicuously or inconspicuously determinate, often strongly ascending, 1–3-forked.
delicate, papery.
monomorphic, in alternate pseudowhorls of 5, tightly appressed, ascending, green, linear-lanceolate to narrowly lanceolate, 2–3.5 × 0.35–0.5 mm (smaller on lateral branches);
abaxial ridges prominent;
base cuneate and decurrent to rounded and adnate on young lateral branches or buds, glabrous or sometimes pubescent;
margins long-ciliate, cilia transparent, spreading to ascending, 0.07–0.17 mm;
apex keeled, truncate in profile, obtuse to attenuate;
bristle white to whitish or transparent, puberulent, 0.45–0.8 mm.
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.
solitary, 0.5–2.5 cm;
sporophylls deltate-ovate to ovate-lanceolate, abaxial ridges well defined, base glabrous, margins ciliate, apex truncate in profile, bristled.
axillary, throughout stem length or restricted to proximal 1/3 of stem, 0.05–0.1 mm diam.
borne on upperside of stems, throughout stem length, 0.2–0.37 mm diam.
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.
= 18.
Selaginella apoda
Selaginella sibirica
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.)
Selaginella sibirica is most closely allied to S. rupestris. In addition to differences noted in the descriptions, it can be distinguished from S. rupestris by the numerous marginal cilia on the leaves and by the transparent sporophyll margins; S. rupestris has a variable number (usually few) of marginal cilia and nontransparent sporophyll margins.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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