Biologia 67/5: 867—874, 2012 Section Botany DOI: 10.2478/s11756-012-0076-z Trichome micromorphology of the Chinese-Himalayan genus Colquhounia (Lamiaceae), with emphasis on taxonomic implications Guo-Xiong Hu 1,3 , Teodora D. Balangcod 2 & Chun-Lei Xiang 1 * 1 Key Laboratory of Biodiversity and Biogeography, Kunming Institute of Botany, Chinese Academy of Sciences, 132 Lanhei Road, Heilongtan, Kunming 650201, Yunnan, P. R. China; e-mail: xiangchunlei@mail.kib.ac.cn 2 Department of Biology, College of Science, University of the Philippines Baguio, 2600 Baguio City, Philippines 3 Graduate School of Chinese Academy of Sciences, Beijing 100039, P. R. China Abstract: Trichome micromorphology of leaves and young stems of nine taxa (including four varieties) of Colquhounia were examined using light and scanning microscopy. Two basic types of trichomes were recognized: eglandular and glandular. Eglandular trichomes are subdivided into simple and branched trichomes. Based on the number of cells and trichome configuration, simple eglandular trichomes are further divided into four forms: unicellular, two-celled, three-celled and more than three-celled trichomes. Based on branching configuration, the branched eglandular trichomes can be separated into three forms: biramous, stellate and dendroid. Glandular trichomes can be divided into two subtypes: capitate and peltate glandular trichomes. Results from this study of morphological diversity of trichomes within Colquhounia lend insight into infrageneric classification and species relationships. Based on the presence of branched trichomes in C. elegans, this species should be transferred from Colquhounia sect. Simplicipili to sect. Colquhounia. We provide a taxonomic key to species of Chinese Colquhounia based on trichome morphology and other important morphological traits. Key words: Colquhounia; glandular hairs; leaf anatomy; Lamioideae; Yunnan Introduction Trichomes are widespread on stems, leaves, calyces and other vegetative and reproductive parts of lamiaceous plants and are widely used in taxonomic studies (El- Gazzar & Watson 1968, 1970; Abu-Asab & Cantino 1987; Navarro & Oualidi 2000). Taxonomically, tri- chomes are useful not only because of the relative ease with which they may be examined but also because of their universal occurrence, particularly in some groups of Lamiaceae (Metcalfe & Chalk 1950; Mathew & Shah 1983; Cantino 1990; Gairola et al. 2009). Moreover, in Lamiaceae, comparative trichome morphology has re- ceived much attention in systematic studies and results from those studies have been commonly employed as taxonomically useful characters at different levels of classification (Bruni et al. 1987; Demissew & Harley 1992; Servettaz et al. 1992; Marin et al. 1994; Navarro & Oualidi 2000; Giuliani et al. 2008; Baran et al. 2010). Colquhounia Wall. was established on the basis of collections from Nepal (Wallich 1822), which is a Chinese-Himalayan genus (Wu 1991; Wu & Wu 1996) of approximately five species (Mabberley 1997; Harley et al. 2004). The genus Colquhounia is recognized by the following characteristics: shrub or woody climbing plant; leaves and young branches covered with var- ious types of trichomes; verticillasters few flowered, in spikes or capitula; equally 5–toothed calyces; and nutlets winged at apex (Li & Hedge 1994). Human uses of some species of this genus are varied. Schilling (1988) reported horticultural value of some species of Colquhounia based on their colorful flowers and long- lasting anthesis. Additionally, Zhou et al. (2004) and Chhetri et al. (2010) demonstrated that Colquhounia has significance in pharmaceutical applications. In China, there are five species and four varieties recognized from Guizhou, Hubei, Sichuan, Tibet and Yunnan Provinces. These are C. coccinea Wall. var. coccinea, C. coccinea var. mollis (Schlecht.) Prain, C. compta W.W. Sm. var. compta, C. compta var. mekon- gensis (W.W. Sm.) Kudo, C. elegans Wall. var. ele- gans, C. elegans var. tenuiflora (Hook. f.) Prain, C. vestita Wall, C. seguinii Vaniot var. seguinii, and C. seguinii var. pilosa Rehd. Except for C. coccinea var. coccinea, all taxa can be found in Yunnan, which is considered to be the center of origin of the genus (Wu & Li 1977; Li & Hedge 1994). Based on trichome mor- phology of leaves and young stems, Wu & Li (1977) classified species of Colquhounia into two sections: sect. Simplicipili C.Y. Wu & H.W. Li and sect. Colquhou- nia Wall. Section Simplicipili is characterized by having simple hairs, whereas the latter has simple trichomes mixed with branched hairs. Xiang et al. (2010) doc- umented nine trichome types in three studied taxa of * Corresponding author c 2012 Institute of Botany, Slovak Academy of Sciences