Scleropodium Bruch & W. P. Schimper, 1853

The genus Scleropodium reaches its greatest world diversity in California. Here, it grows on a variety of habitats ranging from seasonally dry woodlands, very moist forests, and even grasslands. Various Scleropodium species can be found on soil, rock, tree bases, and submerged in rapidly flowing streams. It is easily recognized as Brachytheciaceae by the pleurocarpous and prostrate habit with the costate leaves having that costa ending in a short spine. The diagnostic character of the genus within the Brachytheciaceae is the julaceous habit – a feature possessed even by the somewhat complanate Scleropodium colpophyllum. A cryptic character of uniform application throughout the genus is the pattern of the enlarged laminal cells of the leaf base covering the adaxial surface of the costa base. Note, however, that this unusual feature is shown by some species of Brachythecium.

Key to Scleropodium Etc.

The mosses included in this section are costate pleurocarps with smooth leaves and julaceous stems and branches. Typically, there is some differentiation of an alar region either of numerous rectangular or quadrate cells. At least the upper leaf margins have some serrulation or serration.

Species included in this key are all in Brachytheciaceae:
Cirriphyllum cirrosum (Schwägrichen in Schultes) Grout, not known from CA
Pseudoscleropodium purum (Hedwig) Fleischer in Brotherus
Scleropodium californicum (Lesquereux) Kindberg
Scleropodium cespitans (C. Müller Hal.) L. Koch
Scleropodium colpophyllum (Sullivant) Grout
Scleropodium julaceum E. Lawton
Scleropodium obtusifolium (Mitten) Kindberg in Macoun
Scleropodium touretii (Bridel) L. Koch

A. Interior basal cells of leaf strongly porose; leaves decurrent; plants large with leaves mostly more than 2 cm long; leaf apices narrowed to a long acumen or short apiculus .....B
A. Interior basal cells of leaf not porose; rather thin-walled and somewhat inflated if plant is large; leaf apices various .....C

B. Leaves with an abrupt short and reflexed acumen; plant restricted to lawns and similar disturbed areas .....Pseudoscleropodium: P. purum
B. Leaves with a very narrow long acumen which is at least 1/4 the length of the deeply concave main portion of that leaf; plant of wet and forested areas .....Cirriphyllum: C. cirrosum not known from CA

C. Leaves 0.6-1.4 mm wide; cells across the leaf base rectangular (6-10:1) in one or two series .....D
C. Leaves 0.3-0.8 mm wide; cells across the leaf base quadrate to short-rectangular (1-3:1) in up to six series .....G

D. Branches variable with some leaves spreading to erect-spreading and only faintly concave while other branches are strongly julaceous .....Scleropodium colpophyllum
D. Branches on the entire plant similar and strongly julaceous .....E

E. Leaves on at least some stems with a short-acuminate, recurved apiculus; plant not aquatic but normally on moist soil .....Scleropodium touretii
E. Leaves never with a recurved apiculus; plant typically aquatic and usually in flowing water .....F

F. Leaves orbicular or nearly so; plant with even the ultimate branchlets rigidly spreading ..... Scleropodium species A
F. Leaves about 1.5 times as long as broad; plant flaccid, especially the ultimate branchlets .....Scleropodium obtusifolium

G. Leaves broadest near the base and gradually tapering to the acute apex; stems not very julaceous but growing in thin, straggling mats; seta papillose throughout; capsule curved and asymmetric .....Scleropodium californicum
G. Leaves broadest at about 1/3 and more or less abruptly contracted to the somewhat obtuse apex; stems, seta and capsule various .....H

H. Branches strongly julaceous; capsule curved and asymmetric .....Scleropodium julaceum
H. Branches usually weakly julaceous; capsule erect to inclined .....Scleropodium cespitans