Stems creeping, cespitose, erect, climbing, or vinelike, upperside and underside structurally different, usually highly branched, articulate or not; vessel elements absent. Rhizophores borne on underside or upperside, or in axils of branch forks, always present. Leaves of different shapes and sizes, in 4 ranks (2 median, 2 lateral), linear-lanceolate to ovate, thin and papery to thick and stiff, margins entire, dentate, or ciliate; stomates arranged throughout abaxial surface or sometimes also on adaxial surface; axillary leaves present. Strobili usually quadrangular, sometimes flattened. Sporophylls highly differentiated from the vegetative leaves, most sporophylls fertile (strobili with only 1 basal megasporangium in S. kraussiana), seldom with megasporophylls larger than microsporophylls, in 4 alternating ranks, with or without prominent auricles.

Distribution

Tropical and subtropical regions.

Discussion

Selaginella subg. Stachygynandrum is treated here in the broad sense, including Selaginella eatonii and species belonging to the Selaginella apoda complex.

Previous to J. G. Baker (1883, 1887), and more recently to A. C. Jermy (1986, 1990b), all species with dimorphic vegetative leaves were placed in Selaginella subg. Heterophyllum (Spring) Hieronymus. These species are now referred to each of the currently recognized subgenera (e.g., subg. Stachygynandrum, subg. Heterostachys), according to Jermy's system. Selaginella subg. Stachygynandrum has priority over subg. Heterophyllum.

Species probably more than 650 (11 in the flora).

Selected References

Buck, W. R. and T. W. Lucansky. 1976. An anatomical and morphological comparison of Selaginella apoda and Selaginella ludoviciana. Bull. Torrey Bot. Club 103: 9--16.

Buck, W. R. 1977. A new species of Selaginella in the Selaginella apoda complex. Canad. J. Bot. 55: 366--371.

Buck, W. R. 1978. The taxonomic status of Selaginella eatonii. Amer. Fern J. 68: 33--36.

Somers, P. and W. R. Buck. 1975. Selaginella ludoviciana, S. apoda and their hybrids in the southeastern United States. Amer. Fern J. 65: 76--82.

Somers, P. 1982. A unique type of microsporangium in Selaginella series Articulatae. Amer. Fern J. 72: 88--92.

Webster, T. R. 1990. Selaginella apoda X ludoviciana, a synthesized hybrid spikemoss. Amer. J. Bot. 77(6,suppl.): 108.

Lower Taxa

Selaginella apoda, Selaginella braunii, Selaginella douglasii, Selaginella eatonii, Selaginella eclipes, Selaginella kraussiana, Selaginella lepidophylla, Selaginella ludoviciana, Selaginella pilifera, Selaginella uncinata, Selaginella willdenowii

Key

1	Stems articulate or swollen; rhizophores on upperside of stems; strobili with only 1 basal megasporangium; megasporophylls larger than microsporophylls.	Selaginella kraussiana
1	Stems not articulate; rhizophores on underside of stems, axillary, or seldom on upperside (S. lepidophylla); strobili with many megasporangia, megasporangia basal or throughout length of strobilus; megasporophylls and microsporophylls similar (except in S. apoda complex).	> 2
2	Stems tufted, curling inward when dry, rosette-forming; leaves thick and stiff; growing in seasonally dry and exposed areas.	> 3
2	Stems prostrate, creeping or erect, never rosette-forming; leaves delicate, papery; growing in mild humid areas, very often in shady places.	> 4
3	Median leaves ovate-deltate to deltate, apex acuminate; margins with wide transparent portion, ciliate at base and dentate or ciliate toward apex; base nearly cordate.	Selaginella lepidophylla
3	Median leaves lanceolate (slightly falcate), apex long-bristled, bristle 1/3–1/2 length of leaf; margins with narrow transparent portion, entire or with scattered teeth; base rounded to truncate.	Selaginella pilifera
4	Plants with large aerial, erect, vinelike (high climbing) stems, or bushy.	> 5
4	Plants with rather short-branched, prostrate or creeping stems.	> 6
5	Stems mostly erect, covered with stiff hairs; median leaves long-acuminate to bristled; base of axillary leaves truncate.	Selaginella braunii
5	Stems vinelike, climbing, or shrublike, without hairs; median leaves acute, tip rounded; base of axillary leaves with 2 auricles.	Selaginella willdenowii
6	Margins of lateral leaves entire or basally ciliate; stems long-creeping, lateral branches 2–3-forked.	> 7
6	Margins of lateral leaves dentate to serrate; stem short-creeping or long-creeping (as in S. ludoviciana), lateral branches 1–2-forked.	> 8
7	Median leaves cuspidate with 2 ciliate auricles at base, outer auricle larger and more ciliate than inner auricle; lateral leaves ciliate at base; margins green.	Selaginella douglasii
7	Median leaves acuminate, without auricles; lateral leaves not ciliate; margins transparent.	Selaginella uncinata
8	Median leaves linear or narrowly lanceolate, 0.7–1.2 mm; apex long-bristled; plants minute, forming small mats less than 6 cm diam.	Selaginella eatonii
8	Median leaves ovate to ovate-lanceolate, (1–)1.25–1.5(–1.8) mm; apex acute to acuminate; plants not minute, forming mats larger than 6 cm diam.	> 9
9	Leaf margins with 3–5 rows of transparent cells; stomates of lateral leaves confined to midrib region on adaxial surface.	Selaginella ludoviciana
9	Leaf margins undifferentiated in color or with 1(–2) rows of slightly paler cells; stomates of lateral leaves scattered over adaxial surface.	> 10
10	Median leaves with long-attenuate, veined apices.	Selaginella eclipes
10	Median leaves with acute apices or, if attenuate, usually keeled and without midrib extension.	Selaginella apoda