New Bornean Acanthaceae

Descriptions are given of the tribe Lepidagathideae, that had already been proposed in an earlier paper, and of an entirely new tribe related to the latter, the Borneacantheae. The last-named tribe comprises so far but a single genus, Borneacanthus, based on B. grandifolius; it further includes B. angustifolius, B. paniculatus, B. stenothyrsus, B. parvus and B. mesargyreus (Hall. f.) Brem. (Strobilanthes mesargyreus Hall. f. = Filetia mesargyrea Brem.), and is confined to Borneo. Another new genus, Cosmianthemum, a near ally of Pseuderanthemum, seems to have an even narrower geographical distribution, for it has been found so far only in the western part of Borneo. It is based on C. magnifolium, and comprises in addition C. latifolium, C. angustifolium, C. obtusifolium, C. longibracteatum, C. brookeae, C. punctulatum and C. subglabrum. To the species of these two genera keys are provided. Further are described Hemigraphis sarawacensis, Lepidagathis marginata, Filetia brookeae, F. lanceolata, Hallieracantha peranthera and Peristrophe monosemaeophora. The area of Hallieracantha is extended to Siam by the inclusion of H. graphocaula (Imlay) Brem. ( Justicia graphocaula Imlay). On account of the presence of two different kinds of pollen in this genus, it is suggested that it may not be an altogether natural unit. The leaves of the two new species of Filetia proved to contain inulin, but this substance, whose occurrence in the Acanthaceae was so far unknown, is not present in all the representatives of this genus.