Notes relating to the Flora of Bhutan: XXIX. Acanthaceae, with special reference to Strobilanthes

Abstract

Various problems and issues in the Acanthaceae of Bhutan and the Himalaya are considered. The typification of Thunbergia grandiflora is discussed, and T. lacei and T. clarkei are reduced to synonomy. A new species of Eranthemum, E. erylhrochilum, is described, and the characters which separate it from its allies are listed. A new combination, P. gomezii, is made in Phlogacanthus. The genus Echinacanthus is reviewed and redefined. One group of species placed in it is moved to a new genus, Clarkeasia. which contains one species with two recognized varieties. The Chinese species, Strobilanthes lofuensis, is moved to Echinacanthus pending a thorough review of the three Chinese species in the genus. A wide-ranging discussion of Strobilanthes is presented, and Bremekamp's division of the genus into some fifty segregate genera is criticized and rejected. Various characters used in dividing the genus including life form (with particular attention to the gregarious flowering of the many plietesial species), anisophylly, inflorescence type, calyx development, corolla shape, pollen and seeds are discussed and reassessed. Although pollen is of minor value in subdividing the genus in the Himalayan region, it is possible to recognize 17 distinct groups of species at infrageneric level. These groups are described and discussed with the hope that they will help towards the reclassification of the Strobilanthes group as a whole. Keys are provided for most groups covering species from outside the Himalayan region as well. Thirty-five individual species of Strobilanthes are discussed, of which 17 are described as new. SEM photographs and line drawings illustrate the new species and various aspects of the genus discussed in the paper.