Nutlet morphology in Hemigenia R.Br. and Microcorys R.Br. (Lamiaceae) G. R. Guerin Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, University of Adelaide, S.A Australia Received May 6, 2004; accepted February 8, 2005 Published online: June 22, 2005 Ó Springer-Verlag 2005 Abstract. Nutlets of Hemigenia R.Br. and Micro- corys R.Br. were examined using SEM. Significant variation, mainly useful at the infrageneric level, was found in nutlet shape, nature of the attachment scar, nature of surface sculpturing, exocarp cell shape and sculpturing, and nature of the indumen- tum. Typical nutlets are ovoidal, strongly reticulate or rugose. The exocarp cells are isodiametric and convex to papillate. Also common are cylindrical nutlets, often with longitudinal ridging and papil- late exocarp cells. Surface pitting and concave exocarp cells are rare. A cladistic analysis of nutlet characters suggests both Hemigenia and Microco- rys are polyphyletic, and Microcorys paraphyletic with respect to Westringia Sm. Notwithstanding that, the infrageneric classification of Hemigenia was largely supported, while in Microcorys, there was support for sect. Hemigenioides, but sects. Anisandra and Microcorys were not resolved as distinct. Key words: Hemigenia, Microcorys, Westringieae, Lamiaceae, nutlet, SEM, micromorphology, cladistics. Introduction Use of micromorphological characters in cla- distic analyses and classification within the Lamiaceae is growing (Cantino 1990, Husain et al. 1990, Marin et al. 1994, Oran 1996). Pollen, leaf surfaces, and nutlets have been surveyed. Surface features of seeds and nutlets have been used successfully in a range of systematic studies, and scanning electron microscopy (SEM) has aided character evalu- ation (Barthlott 1984, Mathews and Levins 1986, Stace 1989, Husain et al. 1990, Stuessy 1990, Hedge 1992, Marin et al. 1994, Oran 1996). Taxonomically useful characters include surface sculpturing, nature of the exocarp cells, internal anatomy, and indumentum (Roth 1977; Barthlott 1981, 1984; Stace 1989), and these characters are applicable in Lamiaceae (Hedge 1992). Nutlet characters can be used successfully at many taxonomic levels, depending on the characters chosen and the variation present. However, some characters may not be homol- ogous. Trichomes on fruits are known to be involved in seed dispersal (anemochory or zoochory). For example, glandular trichomes may stick to animal fur (epizoochory; Bouman and Meeuse 1992), and tufts of trichomes on the apex of many Lamiaceae nutlets are likely to have evolved several times (Paton 1992, Marin et al. 1994, Werker 2000). Sculpturing Pl. Syst. Evol. 254: 49–68 (2005) DOI 10.1007/s00606-005-0311-y