Premna Linnaeus has been transferred from the family Verbenaceae to Lamiaceae. Premna is considered one of the fifth largest genera with 46 species in the mint family of the flora of China. Though some regional revisions of Premna have been done, the complete revision of the genus is missing. So it still ranks among the most taxonomically difficult and complicated genera of Lamiaceae.
Mr. TAN Yunhong of Xishuangbanna Tropical Botanical Garden (XTBG) and his colleague conducted a study to deal with the complete taxonomic treatments, geographic distributions and ecological observations of two related taxa: P. fulva and P. tapintzeana.
Field investigations were carried out mainly in Yunnan and Guangxi provinces of China from 2009 to 2012. The distribution map was prepared using geo-referenced locations, data obtained from herbarium specimens and relevant literature (extrapolated or approximated for a few old or vaguely specified localities) and field observations.
In their study, based on protologues, and consulting both herbarium (including the types) and fresh specimens, P. crassa was reduced to synonymy of P. fulva; P. calcicola (ined.), P. crassa var. bijiangensis (ined.), P. crassa var. yuii, P. dopii, P. puerensis, P. shunningensis (ined.), P. straminicaulis, P. yuanjiangensis (ined.) and P. yunnanensis (nom. illeg.) were recognized as P. tapintzeana.
According to the study, Premna fulva and P. tapintzeana are similar to each other by having small corymbs, subequal stamens enclosed by the corolla tube, and equal or slightly 2-lipped calyces with 5 obtuse lobes, but also different in the shape of leaf blades and upper corolla lips, the indumentum of branchlets, petioles and peduncles, and their habitat.
The study entitled “Taxonomic studies on the genus Premna (Lamiaceae) in China—I: the identities of P. fulva and P. tapintzeana” has been published in Phytotaxa.
A fruitescence of Premna fulva
An inflorescence of Premna fulva
A flower of Premna tapintzeana
A fruit of Premna tapintzeana
(Images by TAN Yunhong)