XX. HAPLOCLADIUM (Müller Hal.) Müller Hal., Hedwigia 38: 149. 1899 * [Greek, haplo, once, and cladium, branchlet, alluding to only once-pinnate branching]
Robert E. Magill
Hypnum subsect. Haplocladium Müller Hal. Linnaea 42. 459. 1879
Plants small to medium sized, olive-green, yellow-green to brownish, in dense mats, prostrate. Stems pinnately to sub-pinnately branched, primary stems sometimes becoming stoloniferous with age, branches spreading to ascending; paraphyllia few or abundant, filamentous to subfoliose, frequently branched, pseudoparaphyllia filamentous; rhizoids sparse, often arising from axils of older leaves. Leaves dimorphic, stem leaves erect to curved or subsecund when dry, erect-spreading when wet, oval to ovate, abruptly short or long acuminate, lamina plicate or smooth; margins plane to somewhat recurved at base, smooth to serrulate; costae single, strong, weakly flexuose distally, subpercurrent; median laminal cells rectangular to rhomboidal, 2--4:1, smooth, thin to firm walled but rarely incrassate, 1-papillose over the lumen or prorulose at distal end, distal laminal cells mostly smooth, proximal cells papillose, alar cells little differentiated to quadrate; branch leaves smaller, with more strongly serrate margins and more strongly papillose laminal cells. Specialized asexual reproduction lacking. Sexual condition autoicous. Seta elongate, smooth, frequently flexuose. Capsule curved, horizontal, strongly contracted below mouth when dry, operculum conic; annulus present; peristome perfect, teeth densely cross striate-papillose below, papillose above; endostome as long as exostome, basal membrane high, segments broad, keeled, perforated, cilia well developed, 2--3, nodose; operculum short rostrate; calyptra cucullate, smooth. Spores small, granulate to nearly smooth.
Species 17 (3 in the flora): growing on
rock, humus, wood, and soil worldwide except
Species of Haplocladium resemble those of Thuidium (Chryso-hypnum) but are only once pinnate, have fewer paraphylla and the apical leaf cell has a single papilla at the tip.
2. Stems regularly pinnate; branch leaves oval, acute to apiculate, leaf cell papilla over lumen ………………………………..……..2. Haplocladium virginianum
2. Stems irregularly pinnate; branch leaves oval to ovate, acuminate, leaf cell papilla shifted distally …………………..……3. Haplocladium angustifolium
1. Haplocladium microphyllum (Hedwig) Brotherus, Natürl. Pflanzenfam. 1(3): 1007. 1907
Hypnum microphyllum Hedwig, Sp. Musc. Frond. 269, plate 69, figs. 1--4. 1801
Plants medium sized. Stems somewhat irregularly branched, leaves somewhat distant, paraphyllia small, few to abundant, filamentous and infrequently branched. Leaves erect, broadly ovate to triangular, acuminate, 0.8--1.5 mm, acumen frequently flexuose when dry; margins serrulate throughout, plane but somewhat recurved at base, weakly decurrent; costa ending in acumen or subpercurrent; branch leaves smaller, erect-catenulate dry, erect-spreading wet, ovate, acute to acuminate, 0.5--0.7 mm; median laminal cells subquadrate, sub-rhombic to very short-rectangular, 1.5--2:1, almost smooth to papillose with a single papilla over lumen or shifted distally, proximal cells short-rectangular, smooth, frequently reddish, alar cells quadrate. Capsule inclined to horizontal, oblong, 1.5--2 mm, arcuate. Spores 8--12 \um, almost smooth.
Capsules mature all seasons; damp wood, rocks, humus and soil in wooded situations. Widespread in the northern hemisphere, sea level to upper elevations (0--2500 m); B.C., Alta., Man, Ont., Que.; Ala., Ark., Ariz., Del., Fla., Ga., Ill., Ind., Iowa, Kans., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.Mex., N.Y., N.C., N.Dak., Ohio, Oreg., Pa., S.C., Tenn., Tex., Vt., Va., Wash., W.Va., Wis.; Mexico: West Indies; South America; Eurasia.
The most commonly encountered Haplocladium in North America, H. microphyllum is recognized by the frequently plicate base of the stem leaves, somewhat distant leaves when compared to the other species, and filamentous, little-branched paraphyllia that may be few and scattered or occasionally more common. Paraphyllia on the other two species are much more abundant, frequently branched and more commonly two or more rows of cells wide.
2. Haplocladium virginianum (Bridel) Brotherus, Natürl. Pflanzenfam. 1(3): 1007. 1907
Hypnum virginianum Bridel, Bryologia Universa 2: 576. 1827
Plants small to medium sized. Stems regularly branched, leaves dense, branches julaceous; paraphyllia abundant, filamentous to subfoliose, frequently branched. Leaves erect to erect spreading, ovate, abruptly acuminate, not plicate, 0.5--0.7 mm; margins plane, weakly serrulate throughout; costa ending in apex; branch leaves crowded, imbricate, erect-spreading wet, weakly concave, oval, acute to apiculate or short-acuminate, 0.2--0.5 mm; median laminal cells rounded quadrate, incrassate, strongly papillose with single papilla over lumen, basal and alar cells not differentiated. Capsule curved. Spores 11--12 \um, weakly granulate.
Capsules mature spring--late summer; soil, wood, and rocks of mesic habitats, sea level to moderate elevations (0-1200 m); Ont.; Ark., Conn., Fl., Ga., Ill., Iowa, Kans., La., Md., Mass., Mich., Minn., Mo., Nebr., N.J., N.Y., N.C., Ohio, Okla., Pa., Tenn., Tex., Va., Wash., W.Va, Wis.; c Europe.
Haplocladium virginianum is more regularly branched that the other two species while its crowded, rounded branch leaves have a shorter apex. The small leaf cells and relatively large single papilla centered over the lumen will also help to identify this species.
3. Haplocladium angustifolium (Hampe & Müller Hal.) Brotherus, Natürl. Pflanzenfam. 1(3): 1008. 1907
angustifolium Hampe & Müller Hal., Bot. Zeit.
Plants small. Stems irregularly branched, paraphyllia few, scattered, mostly subfoliose, branched. Leaves dense, imbricate, spreading wet, stem leaves erect, broadly ovate, abruptly acuminate, not plicate, 0.6--0.8 mm, margins plane, serrulate throughout; costa percurrent, filling acumen; branch leaves crowded, imbricate, erect-spreading wet, weakly concave in base, oval to ovate, acuminate, 0.2--0.5 mm; median laminal cells quadrate, little thickened, papillose with single papilla over lumen but this shifted distally, basal and alar cells not differentiated. Capsule with erect base but curved horizontally at about mid capsule. Spores 10--14 \um, weakly granulate.
Capsules mature late summer; wood and humus or rock at higher elevations, moderate to high elevations (800--2000 m); Ariz., N.Mex.; Mexico; West Indies; c Europe; Asia; Africa.
Haplocladium angustifolium occurs in many of the same areas as H. microphyllum but is easily separated by it abundant, subfoliose paraphyllia and stronger branch leaf papillae. It is more likely to be confused with H. virginianum but the two are distinct in their branching patterns, different branch leaf apices and leaf cell papillae. These two species are not currently known from the same area in the flora region.