2. Haplocladium (Müller Hal.) Müller Hal., Hedwigia. 38: 149. 1899. • [Greek, haplos, simple, and kladion, branchlet, alluding to 1-pinnate branching].
Robert E. Magill
Hypnum subsect. Haplocladium Müller Hal., Linnaea 42: 459. 1879
Plants small to medium-sized, in dense mats, olive green, yellow-green, or brownish. Stems pinnate to subpinnate; paraphyllia few or many, filamentous to subfoliose, cells papillose; rhizoids often arising from axils of older leaves. Stem and branch leaves dimorphic. Stem leaves erect, curved, or subsecund when dry, erect-spreading when moist, ovate to sometimes triangular, plicate or not; margins plane to somewhat recurved basally, weakly serrulate to serrulate, ; apex abruptly short- or long-acuminate, hair-point absent; costa single, ending in apex or subpercurrent, , weakly flexuose distally; alar cells little differentiated to quadrate; medial laminal cells rectangular to rhomboidal, smooth, 1-papillose over lumen, or prorulose at distal end, walls thin to firm, rarely incrassate. Branch leaves smaller; margins more strongly serrate; laminal cells more strongly papillose. Specialized asexual reproduction absent. Sexual condition autoicous; perichaetial leaves pale, erect, longer, apex narrowly long-acuminate. Seta1.5-3 cm. Capsule erect, inclined, or horizontal, oblong, curved; annulus present; operculum conic, short-rostrate; peristome perfect; exostome teeth lanceolate, densely cross striate-papillose proximally, papillose distally; endostome basal membrane high, segments broad, cilia well developed. Spores 8-14 µm, granulate to nearly smooth.
Species 17 (3 in the flora): nearly worldwide except Antarctica.
Haplocladium occurs on rock, humus, wood, and soil in open woodland habitats. The genus resembles Thuidium (Chryso-hypnum) but is only 1-pinnate, has fewer paraphyllia, and the apical laminal cell has a single papilla at the tip. The paraphyllia are filamentous; the proximal laminal cells are papillose and the distal cells usually smooth; the seta is smooth and frequently flexuose; the capsules are strongly contracted below the mouth when dry; and the endostome has nodose cilia in groups of two or three.