Inflorescence Odour of the Foul-Smelling Aroid Helicodiceros muscivorus

Abstract

Summary. Chemical analysis of the strong carrion odour produced by an inflorescence of Helicodiceros muscivorus (L. f.) Engl. (Araceae) revealed that the major components were dimethyl disulphide and dimethyl trisulphide. Dimethyl oligosulphides appear to be characteristic constituents of carrion-like floral odours. which to attempt characterisation of the odour chemicals associated with a pollination syndrome. Few carrion-like floral odours have been analysed chemically. In those that have, namely the odours of some Amorphophallus and Pseudodracontium species (Araceae) and Hydnora africana Thunb. (Hydnoraceae), dimethyl oligosulphides have been found to be either the major constituents or the only detectable constituents of the odour (Kite & Hetterscheid 1997, Burger et al. 1988). Apart from various species of Amorphophallus, another member of Araceae that is known for its large inflorescences and strong, foul odour is Helicodiceros muscivorus (L. f.) Engl. (Willis 1952). The species is restricted a few sites in the Balearics and the islands of Corsica and Sardinia where it occurs on rocky slopes and cliffs close to the sea, often in the proximity of gull colonies (Boyce 1994). The inflorescence consists of a large (c. 30 cm diameter), hairy spathe which opens from a long contorted spathe tube and surrounds the densely-hairy spadix. The spathe is coloured pale cream with brownish-purple spots while the spadix is purple. The odour, emanating from the spadix for a few hours after spathe opening, has been described as being of strong carrion (Vogel 1990) or rotting fish, dung or carrion (Boyce 1994). The flowering of H. muscivorus cultivated at the Royal Botanic Gardens, Kew, presented the opportunity to determine whether the chemical composition of its odour was similar to other carrion-mimicking species examined so far.