Contributions to the Morphology of Some Species of Microsorium

Abstract

Morphology of eleven epiphytic and rupicaulous species of Microsorium is described. The paleae in the genus are either peltate with the basal region developing secondarily as a hood over the stalk, or basally attached with auricles on either side of the stalk. The auricles in M. hancockii and M. pteropus develop from single initial cells adjacent to the stalk, while in the others no specialized initial cells occur. Marginal and terminal glandular hairs occur on the paleae, except in M. hancockii and M. pteropus in which marginal hairs are absent. Slender sclerenchyma strands are scattered profusely in the ground tissue of the rhizome. The stelar cylinder is dictyostelic and is dissected by lacunae into cylindrical vascular bundles. Leaf traces are multiple strands originating as branches from the dorsal median vascular bundle of the stelar cylinder and the one next to it on each side. Two or three closely placed vascular bundles of the rhizome constitute the vascular connexion to each branch of the rhizome. Venation of the leaf lamina is reticulate with most of the free-ending veinlets entering foliar hydathodes. The juvenile leaves bear hairs similar to the pro-thallial hairs and are spatulate with a medianly placed forked vein. Sori are generally punctiform, but in M. hancockii and M. pteropus spread slightly over the veins, often forming elongated coenosori. Uniseriate (multiseriate in M. rubidum), multicellular paraphyses occur in all species except M. scolopendria. The spores are monolete and either psilate or granulate. The prothalli develop from 3-5 cells long germ filaments in which the anterior cells divide longitudinally and form an ameristic prothallial plate. An apical meristematic cell is formed later, and a cordate prothallus is developed, except in M. hancockii and M. pteropus in which a definite meristem is never formed and the prothalli are ribbon-shaped and branched. The cordate prothalli possess polypodiaceous hairs: the ribbon-shaped ones are more or less naked and devoid of any midrib. The chromosome number in the species is n = 36 (zn = 72).