Published In:
Bryologia Universa 2: 671. 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:
Phyllogonium has three species, all of which are found in Central America. The genus is distin-guished by its golden brown to olive green plants that typically form festoons on the branches of trees and shrubs, but on occasion can be terrestrial. Secondary stems and branches are densely foliate, with distichous, equitant, conduplicate, and cucullate leaves. The leaves are more or less auriculate, with differentiated alar regions, and linear-repand, porose median laminal cells. Differences in their leaf apices are the best means of distinguishing the species. In P. fulgens and P. viride, the apices are pun-gent, the former retuse-erect and the latter strongly recurved but not retuse. In P. viscosum, the leaf apices are truncate. Unfortunately, the leaf apices in all three species are somewhat variable. For ex-ample, in P. fulgens the pungent apices can be somewhat curved, in P. viride some apices can be re-tuse, and in P. viscosum some apices can be somewhat pungent. According to Buck (1998), the pri-mary stems turn about 90/ to give rise to pendent secondary stems; the primary stems then continue forward growth by buds that form near the base of secondary stems. Fecundity is very low in the genus as a result of the dioicous condition of the plants. Asexual propagation, although not demon-strated, is probably by fragmentation of leaves and leafy branches. The name Phyllogonium combines the Greek phyllo (leaf) with gonia (angled or angular); ac-cording to Bridel (1827), the name refers to the inclusion of the female gametangia within the dou-bled or conduplicate leaves.
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Plants medium-sized to robust, lustrous, golden brown to olive green, sometimes dark brown to black, especially in older parts, usually in complex festoons on limbs and branches, occasionally terrestrial. Primary stems dark castaneous, prostrate, attached tightly to substrate, irregularly branched, with small, fragile, scale-like leaves; stems in cross section with small incrassate cells enclosing larger thin-walled cells, central strand absent; rhizoids smooth, castaneous, in clusters basal to dorsal sides of leaves. Secondary stems and branches densely foliate, irregularly branched, pendent; para-phyllia none; pseudoparaphyllia foliose; axillary hairs with 1–3 more or less quadrate, pigmented basal cells and 2–5 elongate, hyaline distal cells, distalmost cells obtuse to rounded; rhizoids similar to those of primary stems. Secondary stem and branch leaves altered little when dry, erect-spreading, smooth or undulate, distichous, equitant, conduplicate, oblong, more or less auriculate, cucullate, truncate to retuse-pungent and erect to strongly pungent and recurved but not retuse; margins more or less entire, incurved distally; costae weakly short and double or absent; cells unistratose, smooth, linear-flexuose, shorter distally and proximally, more or less incrassate, porose; alar cells differenti-ated, in small, dark patches; leaves of flagelliform branches erect-spreading, sometimes more or less appressed, concave, not conduplicate, pungent to acuminate. Asexual propagula none. Dioicous. Perichaetia and perigonia gemmiform, axillary, inconspicuous or conspicuous; perichaetial leaves more or less convolute, oblong-ovate, concave, not conduplicate, abruptly acuminate; perigonial leaves oblong-ovate, concave, acuminate. Setae short, smooth, dark castaneous; vaginulae more or less pilose. Capsules shortly exserted or immersed, erect, radially symmetric, cylindric to urceolate, castaneous or pale yellow; exothecial cells irregularly quadrate to irregularly oblong, incrassate, walls evenly thickened; stomata phaneroporous in proximal parts or absent; opercula conic, obliquely long-rostrate; annuli of 1–3 tiers of incrassate, oblate cells. Peristome diplolepideous, double or single, in-serted just below capsule mouth, prostome sometimes present, exostome inflexed when dry, erect when moist, teeth pale, margins irregular, smooth to finely papillose, ventral trabeculae well devel-oped; endostome (lacking in P. viride) greatly reduced, basal membranes low, segments rudimentary. Spores more or less spherical, finely papillose to verrucose. Calyptrae cucullate or mitrate, naked or more or less pilose.
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