Monographs Details: Pinnatella
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants small to robust, stipitate-frondose, in mostly dull, green to yellow-green, often small mats. Primary stems creeping, secondary stems mostly arising from upturning primary stem, the creeping stem continuing by innovations near the base of the stipe, the secondary stems distinctly stipitate, erect to pendent, 1-2-pinnate, ± complanate-foliate, stem apex sometimes becoming flagellate, axillary flagellate branches common; in cross-section with small thick-walled cells surrounding larger thinner-walled cells, central strand present (but apparently absent in slender stolons); paraphyllia absent; pseudoparaphyllia mostly foliose; axillary hairs with a 1-2 short brown basal cells and 1-3 elongate hyaline distal cells. Primary creeping stem leaves reduced, appressed, ovate to triangular, acute to short-acuminate, rarely obtuse, ± decurrent; margins serrulate to subentire above, subentire below, often narrowly recurved at middle or below; costa mostly single, short to strong, rarely absent; cells laxly rectangular, larger than in other leaves. Stipe leaves few, loosely appressed with apices erect to squarrose, ovate to triangular, acute to acuminate, ± decurrent; margins serrulate above, subentire below, usually narrowly recurved below; costa single, usually ca. 3/4 the leaf length (weaker than in stem and branch leaves), sometimes stronger or weaker to absent; cells small, ± isodiametric, smooth, prorulose or unipapillose, thick-walled, ± collenchymatous; alar cells weakly differentiated. Secondary stem (continuation of stipe above branching) leaves mostly complanate, ± erect to erect-spreading, ovate to ovate-ligulate, symmetric to asymmetric, acute to short-acuminate to obtuse, ± concave, sometimes plicate or undulate; margins serrulate above, crenulate to subentire below, plane or narrowly recurved or incurved; costa typically single and ending near leaf apex, sometimes shorter, rarely short and double; cells small, ± isodiametric or rarely elongate, smooth or prorulose, seldom unipapillose, thick-walled, ± collenchymatous, becoming more elongate toward insertion, often with an inframarginal limbidium of ± elongate cells, indistinct, to ca. 4/5 the leaf length; alar cells weakly differentiated except in orientation. Asexual propagula often of flagellate branches with reduced leaves. Dioicous. Perichaetia large and conspicuous, without ramenta; leaves erect, convolute with erect to wider spreading apices, oblong-ovate, acute to broadly acuminate, sometimes obtuse; margins subentire to serrulate above, subentire below, plane; costa mostly single, reaching base of acumen or longer; cells elongate throughout, smooth, thick-walled, ± porose, becoming thinner-walled toward the insertion. Setae short (2-4.5 mm), mammillose above, smooth below or rarely throughout, erect, straight or curved below capsule; capsules erect to suberect, ovoid to cylindric, symmetric; exothecial cells short-rectangular, firm-walled, becoming smaller toward the mouth; annulus not differentiated; operculum obliquely conic-rostrate; peristome double, inserted below the mouth. pale, exostome teeth spiculose-papillose throughout, sometimes perforate, not trabeculate at back; endostome with a low basal membrane, segments slender, spiculose-papillose, keeled, narrowly perforate, ca. as long as the teeth, cilia none or rarely rudimentary. Spores spherical, finely papillose. Calyptrae little known, campanulate (?), hairy at base, smooth.
Discussion:Pinnatella M. Fleisch., Hedwigia 45: 79. 1906; Hypnum sect. Pinnatella Müll. Hal., Linnaea 39: 456. 1875, nom. nud.; Porotrichum sect. Pinnatella Miill. Hal., Linnaea 40: 272. 1876, nom. nud.
Thamnium subgen. Camptolepis Kindb. sect. Leiophylla Kindb., Hedwigia 41: 212. 1902.
Discussion. As recently revised (Enroth, 1994), Pinnatella is a genus of 15 species. It is characterized by stipitate-frondose growth with laminal cells ± isodiametric and often prorulose. The setae are short with erect capsules and papillose peristomes.
Pinnatella differs from Homaliodenclron by the central strand in the stems and the small, prorulose laminal cells. From Porotrichum it may be told by the small, ± isodiametric laminal cells and the short setae. From Thamnobryum it may be distinguished by the small size and papillose peristome. The genus is most diverse in Southeast Asia, with only a single species reaching the Americas.