Cell wall structure of selected epiphytic mosses from a montane forest in the Venezuelan Andes

Cell wall cross sections of 15 mosses from a tropical lower-montane cloud forest were studied using scanning electron microscopy. The ramicolous understorey mosses, of fan, pendant and dendroid life-forms, generally have thick cell walls occupying >30 of the total cross section; the species with the thinnest cell walls, Toloxis imponderosa, has the leaf surface densely covered with papillae. Two basic patterns of cell wall ultrastructure are present in the understorey epiphytic mosses with hanging life forms which, along with the papillose cell walls of T. imponderosa, could be complementary mechanisms for water conduction and retention by pendulous mosses. Species of the forest floor and of the larger branches in the canopy, mostly of mat or turf life-forms, show relatively thinner cell walls.