XVI International Botanical Congess

Nine subgenera of the genus Riccardia are recognized. Among them six subgenera are distributed in Southeast Asia and Oceania: Riccardia, Phycaneura, Hyaloneura, Corioneura, Neoneura and Thornoneura. They are critically separated by the distribution of mucilage hairs on thalli. A new subgenus is provided for Riccardia hydra Huer. from New Caledonia and Borneo. The new taxon has a very unique thalli which is very slender like those of algae, lack medullary cells in ultimate branches and lack mucilage hairs. The bryogeography of those subgenera is discussed. Five out of the nine subgenera (Hyaloneura, Corioneura, Neoneura, Thornoneura, and new one) are endemic to the areas under discussion. This suggests that the mossy forest of Southeast Asia and Oceania is one of the centers of distribution of this genus.