Monographs Details: Vesicularia
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants mostly medium-sized, in somewhat lustrous, flaccid to soft, dark- to pale-green to golden, often extensive, thin mats. Stems creeping, irregularly but freely branched to regularly pinnate, the branches mostly simple, often straight when dry, somewhat curved when moist; in cross-section without a hyalodermis, with small firm-walled cells surrounding larger firm-walled cells, central strand present or absent; pseudoparaphyllia filamentous to narrowly foliose (biseriate); axillary hairs with a single short brown basal cell and several elongate hyaline distal cells. Stem and branch leaves differentiated, crowded to lax, often contorted when dry, sometimes falcate-secund, stem leaves broadly inserted, the lateral and ventral ones similar, the dorsal ones somewhat shorter pointed and with laxer areolation, ovate-lanceolate to broadly ovate, acute to acuminate; margins entire to serrate, plane; costa short and double or absent; cells hexagonal to sublinear, broad, smooth, mostly thin-walled, becoming shorter and rectangular toward the insertion; alar cells not differentiated. Branch leaves often with differentiated ventral leaves, dorsal and lateral leaves lanceolate to ovate, acute to acuminate, sometimes flaccid; margins sometimes obscurely bordered, entire to serrate, plane; costa short and double or absent; cells hexagonal to long-hexagonal, smooth, thin- to firm-walled, becoming shorter and rectangular toward the insertion; alar cells not differentiated; ventral leaves mostly lanceolate, short- to long-acuminate; margins serrulate, plane; costa often lacking; cells longer than in lateral and dorsal leaves. Asexual propagula not seen. Autoicous (except in a single East Indian species). Perichaetial leaves erect, often with spreading apices, oblong-lanceolate, ± abruptly acuminate; margins entire to serrulate to denticulate, plane; costa usually none; cells long-hexagonal in the acumen, shorter and broader in the base, smooth, firm- to thick-walled; alar cells not differentiated. Setae elongate, slender, smooth, reddish, flexuose, curved just below the urn; capsules horizontal to pendent, short, ovoid to short-cylindric, ± symmetric, sometimes constricted below the mouth when dry; exothecial cells quadrate to rectangular, thin-walled, often collenchymatous; annulus differentiated; operculum apiculate to short conic-rostrate; peristome double, exostome teeth shouldered, bordered, on the front surface cross-striolate below, coarsely papillose above, trabeculate at back; endostome with a high basal membrane, segments broad, keeled, narrowly perforate, ca. as long as the teeth, cilia in groups of 1-3. Spores spherical, finely papillose, small. Calyptrae cucullate, naked, smooth.
Discussion:Vesicularia (Müll. Hal.) Müll. Hal., Bot. Jahrb. Syst. 23: 330. 1896; Hypnum sect. Omalia subsect. Vesicularia Müll. Hal., Syn. Musc. Frond. 2: 233. 1851; Ectropothecium sect. Vesicularia (Müll. Hal.) Renauld, Prodr. Fl. Bryol. Madagascar 253. 1897 .
Acosta Müll. Hal., Linnaea 21: 191. 1848, hom, illeg., non Adans., Fam. Pl. 2: 117. 1763 [Asteraceae], nec Lour., Fl. Cochinch. 276. 1790 [Ericaceae], nec Ruiz & Pav., Fl. Peruv. Prodr. 1. 1794 [Polygalaceae]; Hypnum sect. Acosta (Müll. Hal.) Hampe, Ann. Sci. Nat. Bot. V, 5: 325. 1866.
Discussion. Vesicularia is characterized by differentiated dorsal and ventral branch leaves and all leaves with lax areolation. It might be confused with Leucomium or Rhynchostegiopsis that also have very lax areolations (and live in humid habitats) but in those genera the ventral leaves are not differentiated, pseudoparaphyllia are absent, and the outer stem cells are enlarged. Vesiculada is presumably related to Ectropothecium as evidenced by the short capsules with collenchymatous exothecial cells.
The plants of our local taxa of Vesiculada are very plastic, as might be expected by their affinity for humid environments. Salmon (1904) treated most of the West Indian taxa but seemingly examined only type specimens and some very few others. The plants are much more variable than he would have one believe, and more than one “species” can be found on a single stem. However, his illustrations from type specimens are helpful. As treated here, the genus in the West Indies consists of one polymorphic species with four varieties.