THE GENERA THYSANANTHUS, DENDROLEJEUNEA, AND FULFORDIANTHUS GEN-NOV (STUDIES ON LEJEUNEACEAE SUBFAMILY PTYCHANTHOIDEAE XXI)

The genus Thysananthus (Lejeuneaceae subfam. Ptychanthoideae) has about 10 species in two subgenera and occurs in rain forests throughout the tropics. The center of diversity is in Southeast Asia. Dendrolejeunea and Fulfordianthus are segregated from Thysananthus on the basis of their dendroid growth habit, regularly pinnate branching, and differentiated cortex. Lack of trigones and oil bodies, and pycnolejeuneoid innovations, are the unique features of Fulfordianthus. A key is provided to the genera, subgenera, and species of this complex. Dendrolejeunea is monotypic and Asiatic in distribution whereas Fulfordianthus contains two species endemic to Central America and the Choco region of northwestern South America. These two genera are elements of the shaded understory of old-growth tropical rain forest and their continued existence is threatened by destruction of the forest.