This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
About 340 species, widely distributed, most abundant in the tropics. Besides the following some five others occur in western North America. Type species: Lycopodium sclaginoides L.
Stem-leaves all alike, many-ranked.
Stems compact with rigid leaves; spikes quadrangular.
Stems slender; leaves lax, spreading; spikes enlarged, scarcely quadrangular.
Stem-leaves of 2 kinds, 4-ranked, spreading in 2 planes.
Stems densely tufted, with occasional sterile runners and sub-pinnate branches, i'-3' high, commonly curved when dry. Leaves rigid, appressed-imbricated, 1" or less long, linear or linear-lanceolate, convex on the back, more or less ciliate, many-ranked, tipped with a distinct transparent awn; spikes sessile at the ends of the stem or branches, strongly quadrangular, 6"-12" long, about 1" thick; bracts ovate-lanceolate, acute or acuminate, broader than the leaves of the stem; megasporanges and microsporanges borne in the same spikes, the former more abundant.
Sterile branches prostrate-creeping, slender, ¥-2' long, the fertile erect or ascending, thicker, 1 - 3' high, simple; leaves lanceolate, acute, lax and spreading, sparsely spinulose-ciliate, 1"-2" long; spikes solitary at the ends of the fertile branches, enlarged, oblong-linear, subacute, 1' or less long, 2"-2\" thick; bracts of the spike lax, ascending, lanceolate or ovate-lanceolate, strongly ciliate.
On wet rocks, Labrador to Alaska, south to New Hampshire, Michigan and Colorado. Also in northern Europe, Greenland and Asia. Mountain-moss. Prickly club-moss. Summer.
Lycopodium apodum L. Sp. PI. 1105. 1753. S. apus Spring in Mart. Fl. Bras, 12: 119. 1840.
Annual, light green, stems prostrate-creeping, 1-4' long, much branched, flaccid, angled on the face. Leaves minute, membranous, of 2 kinds, 4-ranked, spreading in 2 planes; upper leaves of the lower plane spreading, the lower reflexed, ovate, acute, serrulate, not distinctly ciliate; leaves of the upper plane ovate, short-cuspidate; spikes 3"-8" long, obscurely quadrangular; bracts ' ovate, acute, sometimes serrulate, acutely keeled in the upper half; megasporanges more abundant toward the base of the spike.
In moist shaded places, often among grass, Maine and Ontario to the Northwest Territory, south to Florida, Louisiana and Texas. Ascends to 2200 ft. in Virginia. July-Sept.