Published In:
Bryologia Universa 1: xlvi; 2: 807, 812. 1827. ( Bryol. Univ.)  
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(Last Modified On 1/29/2014)
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Acceptance
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Accepted
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(Last Modified On 1/29/2014)
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Discussion:
Homalia was revised by He (1997). The genus consists of five North Hemispheric species, only one of which (H. glabella) crosses into the Southern Hemisphere. Gametophytically, the genus is characterized by its glossy, strongly flattened stems that either lack or have a weakly developed cen-tral strand. Its stems are complanate-foliate, with oblong-ovate to oblong-spathulate, plane-margined leaves inserted in 8 ranks. All Homalia species have rounded, obtuse or broadly acute leaf apices and smooth cells that are rhombic to irregularly rhomboidal at the apex. The costae in Homalia vary con-siderably between species; some species have long, single costae, while in others they are short, faint, and can be either single or double on leaves from the same plant. The Homalia sporophytes have long setae, with erect to suberect capsules, well-developed annuli, and stomata. Homalia has a perfect, hypnaceous peristome, with broad exostome teeth that are densely cross-striate on the lower dorsal surface and an endostome with a high basal membrane, broadly perforate segments, and 2–4 well-developed cilia. The systematic position of Homalia within the family is uncertain because it presents the classic moss dilemma: gametophytic features supporting one placement, but sporophytic features that sup-port another. In this case, the gametophytes of Homalia closely resemble the genera associated with the subfamily Neckeroideae, while its sporophytes are identical to those found in the subfamily Thamnioideae. Fleischer (1908), Brotherus (1925), and Walther (1983) have aligned Homalia with the Neckeroideae; Sastre (1987) and Gradstein et al. (2001) place the genus in the Thamnobryaceae on the basis of its perfect hypnaceous peristome. However, because of the radically differing rela-tionships implied by the different generations in Homalia, it is impossible to determine its generic re-lationships based solely on morphology. The name Homalia is from the Greek homalos (even or level) and refers to the characteristically flattened stems and branches of this genus.
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Plants small to large, strongly flattened, dark green to yellowish green, at times yellowish red, glossy. Primary stems creeping, often stoloniferous; rhizoids smooth, reddish brown, densely present on stolons and at the base of secondary stems; leaves appressed to spreading, oblong-ligulate. Sec-ondary stems prostrate, not stipitate, irregularly branched, complanate-foliate, at times flagellate-attenuate; secondary stem cross section with sclerodermis, cortical cells enlarged, thick-walled, central strand absent or weakly developed; paraphyllia absent; pseudoparaphyllia present or absent. Sec-ondary stem and branch leaves strongly flattened, wide-spreading, smooth when dry or wet, oblong, oblong-ligulate, or oblong-spathulate, 1.0–3.0 mm long, asymmetric, mucronate to rounded or trun-cate, apiculate or broadly acute, narrowly decurrent, straight at the insertion; margins inflexed on one side below, serrulate at apex, entire to subentire below; costae single and long, or faint, short, double or single; cells smooth, apical cells rounded, rhombic, or shortly fusiform, firm- to thick-walled, oc-casionally porose, median cells oblong-rhomboidal to linear-rhomboidal, thick-walled, basal juxta-costal cells linear-fusiform, thick- to firm-walled, porose; alar cells rectangular to oblong-rectangular, weakly differentiated, cells across the insertions porose. Asexual propagula absent. Dioicous. Peri-chaetial leaves ovate, sheathing at base. Setae elongate. Capsules erect to suberect, ovoid to oblong-ovoid, or oblong-cylindric, asymmetric; exothecial cells rounded, subquadrate to short-rectangular, firm- or thick-walled; stomata on neck; opercula obliquely long-rostrate; annuli well developed; peri-stome diplolepideous; exostome teeth 16, narrowly triangular, dorsal surface densely cross-striate and papillose below, papillose above in vertical lines, trabeculae and median line well developed; endo-stome basal membranes high, segments subulate, broadly perforate, keeled, cilia well developed, 2–4, nodose or appendiculate. Calyptrae cucullate, smooth.
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