Studies on the leaf structure in some species of Leucobryaceae. III.Leucobryum sanctum(Brid.) Hampe and Leucobryum sp. (Leucobryeae)

Abstract

AbstractThe leaves of Leucobryum sanctum (Brid.) Hampe and Leucobryum sp., two species of wet tropical environments, are homostrosic in structure, exhibit leucocysts with outer walls as thin as the inner ones, and lack surface pores. The comparison with species of Leucobryaceae previously investigated indicates that inter-specific changes in leaf morphology affecting the leucocyst arrangement, the surface porosity and the thickness of outer leucocystwalls may be related to microclimatic conditions. A model is proposed according to which leucocysts and chlorocysts of leucobryaceous mosses would have evolved from stereids and euricysts of the leaf nerve respectively of a ‘pottioid’ and/or a ‘dicranoid’ ancestor. It is suggested that heterostrosic forms are more primitive than homostrosic ones, the latter being derived from the former as a result of the restrictive adaptation to moist habitats.