Swainsona 33: 75–102 (2020) © 2020 Board of the Botanic Gardens & State Herbarium (Adelaide, South Australia) A preliminary survey of the leaf-indumentum in the Australian Pomaderreae (Rhamnaceae) using Scanning Electron Microscopy Jürgen Kellermanna,b a State Herbarium of South Australia, GPO Box 1047, Adelaide, South Australia 5001 Email:
[email protected] b School of Biological Sciences, Adelaide, The University of Adelaide, South Australia 5005 Abstract: The tribe Pomaderreae (10 genera, c. 240 species) is almost endemic to Australia and defined within Rhamnaceae by the presence of ‘stellate hairs’. This paper is the first to report observations on the leaf-indumentum of 33 species of the tribe with Scanning Electron Microscopy. Apart from simple hairs and papillae, three types of stellate trichomes were observed: fasciculate hairs, appressed stellate hairs and multiradiate hairs (sessile or stalked). The existence of stellate trichomes on the examined species of Pomaderreae was confirmed. Trichomes and indumenta are often variable within genera, as the type of indumentum may be more related to its function. Some groups of species in the genera Cryptandra Sm., Pomaderris Labill. and Stenanthemum Reissek have indumentum characters that seem to be more consistent and might be of value to elucidate relationships between taxa. Keywords: Rhamnaceae, Pomaderreae, leaf morphology, trichomes, hairs, leaf surface, SEM Introduction xeromorphic adaptations, such as small, hard, revolute or conduplicate leaves, a dense indumentum or spines. Pomaderreae Reissek ex Endl. is the second largest tribe of Rhamnaceae. It was first described by Reissek On-going molecular and morphological studies in (1840), but not accepted by subsequent botanists (e.g.