Dhofar is a wide region situated in southern Oman, bordering with Yemen and Saudi Arabia. The area is characterised by the presence of a plain which lies along the coast of the Arabian Sea, at the foot of the steep slopes of the escarpment which rise towards the desert plateau of the Arabian peninsula. The coastal plain is in- terrupted by numerous small estuaries of wadies, which are often separated from the open sea by sand barriers and contain fresh water. The coast and the slopes are influenced by Monsoon regime which causes moistness and rains during sum- mer: the clouds are not able to rise over the escarpment and release precipitations on its slopes. The coastal plain is covered by a semi-desert grass- land with scattered small trees and xerophytic shrubs which generally increase towards inland. Wetland vege- tation occurs along wadis and estuaries. In eastern Dho- far, woodlands cover the slopes of the escarpment; scat- tered plants occur on the dry slopes approaching the Yemen border, at west. A Flora of Dhofar was published by Miller and Mor- ris (1988) and many plant groups have been and still are object of investigation. Numerous papers were devoted to the study of Boswellia sacra Flueck., the frankincense tree, a plant economically important for the trade of its Pollen morphology of trees, shrubs and woody herbs of the coastal plain and the monsoon slopes of Dhofar (Sultanate of Oman) M. MARIOTTI LIPPI, T. GONNELLI, M. RAFFAELLI. Dipartimento di Biologia Vegetale dell’ Università Via G. La Pira 4, I-50121 Firenze Accettato il 19 Settembre 2007 Morfologia pollinica di alberi, arbusti e erbe perenni della pianura costiera e dei versanti monsonici del Dhofar (Sultanato di Oman) – Il presente lavoro è dedicato alla morfologia pollinica delle più comuni piante arboree, arbustive ed erbacee perenni che crescono in Dhofar, nell’Oman meridionale. Vengono anche riportate informazioni sull’habitus delle pian- te e sul loro ambiente di crescita. Key word: Dhofar, pollen morphology, Oman, shrubs, trees. resin, from ancient time. B. sacra grows on the arid slopes of western Dhofar, in the mountains near Hasik, and in pre-desert areas at the edge of the Arabian plateau (Thulin & Warfa, 1987; Raffaelli et al., 2003a,b, 2006). An annotated catalogue of the vascular plants of Oman (Ghazanfar, 1992) and a Flora of Oman, including the Flora of Dhofar, is in progress (Ghazanfar, 2003). The pollen morphology of the plants which grow in this area is poorly known. The pollen Flora of Qatar (El- Ghazaly, 1991) is the only exhaustive study in the Ara- bian Peninsula. However, it includes mainly the species occurring in the plateau and covers only a small part of the plants growing in Dhofar. The only other useful ref- erence palynoflora seems to be that of African savanes (Bonnefille & Riollet, 1980). This statement underlines the affinities between Arabian peninsula and East Africa, from a floristic point of view. However, the pollen morphology of many species is still unstudied. Also paleopalinological investigations carried out in southern Oman are scarce (Lezine et al., 2002; Mariot- ti Lippi, 2002; Hoorn & Cremaschi, 2004). The aim of this paper is to improve the knowledge of the pollen morphology of the most common trees, shrubs and woody herbs widespread in the coastal plain and the escarpment of Dhofar (Fig. 1). Webbia 62(2): 245-260. 2007 Centro Studi Erbario Tropicale, Università di Firenze - Pubbl. n. 110.