Homaliodendron

• Authority

  Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.

• Family

  Neckeraceae

• Scientific Name

  Homaliodendron

• Description

  Genus Description - Plants typically robust, stipitate-frondose, in mostly dull, dark-green but becoming yellow-green to golden with age, often extensive colonies. Primary stems creeping, secondary stems mostly arising from upturning primary stem, the creeping stem continuing by innovations near the base of the stipe, but erect or pendent stems sometimes arising laterally, the secondary stems distinctly stipitate, erect to pendent, frondose, 1-3-pinnate, complanate-foliate, axillary flagellate branches common; in cross-section with small thick-walled cells surrounding larger firm-walled cells, central strand none; paraphyllia absent; pseudoparaphyllia filamentous to foliose; axillary hairs with (1-)2(-3) short brown basal cells and (1-)2-7 hyaline distal cells. Primary creeping stem leaves and those of the stipe similar, strongly differentiated from other stem and branch leaves, not complanate, erect-appressed, mostly triangular, gradually to ± abruptly acuminate, not or shortly decurrent; margins mostly subentire, plane to narrowly recurved; costa single, or apparently absent in sect. Circulifolia; cells elongate, smooth, thick-walled; alar cells not or scarcely differentiated. Secondary stem (continuation of stipe above branching) leaves and branch leaves similar but branch leaves notably smaller, complanate, typically wide-spreading, broadly oblong to oblong-ovate to oblong-obovate, asymmetric, mostly acute to short-acuminate but sometimes (sect. Circulifolia) broadly rounded to truncate; margins typically coarsely serrate above with multicellular teeth, but sometimes (sect. Circulifolia) subentire to serrulate, subentire below, mostly plane above, usually inflexed on one side below; costa single, ending above midleaf or seldom lower; cells in apex rounded-rhomboidal, relatively short, mostly 1-3:1, becoming longer at midleaf and even longer toward insertion, smooth or rarely unipapillose, thick-walled, ± porose; alar cells not or scarcely differentiated. Asexual propagula of flagellate branches with reduced leaves, arising apically or from leaf axils. Dioicous. Perichaetia large and conspicuous, without ramenta; leaves convolute below and erect to spreading above, mostly oblong, gradually or abruptly narrowed to a short or long acumen; margins entire to serrate, plane; costa usually absent, sometimes short and single; cells elongate, smooth, thick-walled, becoming laxer toward the insertion. Setae short, typically <5 mm long, smooth, yellowish, straight; capsules exserted, erect to suberect, ovoid to cylindric, symmetric; exothecial cells subquadrate to short-rectangular, thick-walled, becoming smaller toward the mouth; annulus not or weakly differentiated; operculum obliquely short-rostrate from a conic base; peristome double, attached at the mouth, exostome teeth papillose throughout or rarely on front surface at base with faint cross-striolations, not or slightly trabeculate at back; endostome with a mostly low basal membrane, segments slender, papillose, keeled, perforate, ca. as long as the teeth, cilia none. Spores spherical, papillose. Calyptrae cucullate, naked or hairy, smooth.

• Discussion

  Discussion. Homaliodendron is characterized by stipitate-frondose plants with wide-spreading complanate leaves. The stems lack a central strand. The leaves typically are coarsely serrate but one of our species inconsiderately has only serrulate margins. The unicostate leaves have short, thick-walled apical cells, gradually lengthening toward the insertion; alar cells are not or scarcely differentiated. The dioicous plants have short setae (mostly 2-4 mm long) and erect capsules with an obliquely short-rostrate operculum. The exostome is typically papillose throughout and the reduced endostome has a low basal membrane, narrow segments, and no cilia. The calyptrae are cucullate. Homaliodendron may be confused with other stipitate neckeroid mosses. It is distinct on a practical level by the stems lacking a central strand and by the short apical laminal cells. Of little use in identification are the short setae and reduced peristomes since the genus is not known fertile in the New World. The Indochinese species of Homaliodendron were monographed by Ninh (1984) and are of local interest because of the shared H. flabellatum. As noted in the generic description above, the genus seems to have a discordant element segregated as sect. Circulifolia M. Fleisch., known only in the Old World. Additional work may realign it.