456. MUTISIA RETRORSA Compositae Nicholas Hind and Tony Hall Summary. The taxonomic history, cultivation requirements, distribution and habitat of M. retrorsa Cav. are discussed. A full synonymy, description, colour plate, and line drawings of the dissections of this species are given. In the first of three plates on the spectacularly flowered genus Mutisia L.f., that of M. retrorsa Cav. represents species with mid- range capitulum sizes and is one of the yellow-flowered species of sect. Guariruma (Cass.) Cabrera. Mutisia retrorsa was described by Cavanilles (1799) in an account that added another ten species to the genus following its publication in 1781 by Linnaeus son in Supplementum Plantarum. Cavanilles illustrated all his species, together with Mutisia clematis L.f., with a fine set of engravings showing detailed dissections of the capitula alongside habit drawings. We now accept that some of Cavanilles species had earlier names dating from Ruiz & PavÑons account of four new species from Peru and Chile a year before (Ruiz & PavÑon 1798): M. inflexa Cav. (¼ M . subulata Ruiz & Pav.), M. viciifolia Cav. (¼ M . acuminata Ruiz & Pav.), and M. peduncularis Cav. (¼ M . acuminata Ruiz & Pav.). A quick glance at the description below will show that M. retrorsa is one of the taxonomically least problematic species. Cabrera (1971) recognized three varieties, which are relatively easily distinguished by their more marked leaf dissection; both of Cabreras other varieties having profoundly pinnatisect leaf blades. However, recent collections in Prov. CÑordoba, Argentina, (Espinar 2000) have led to the re-recognition of M. castellanosii Cabrera and the recognition of a new variety. Mutisia castellanosii includes the pinnatisect-leaved taxa originally included under M. retrorsa; I am happy to follow Espinars view. The colour of the ray florets is actually rather difficult to describe. The modern RHS colour chart hasnt got a dark enough yellow as a good match but, going back to the old 1938 British Colour Council=Royal Horticultural Society Chart (RHS 1938) the colour match is between aureolin and lemon yellow. The limb of the ray florets is bicolorous and the lower surface is suffused # Royal Botanic Gardens, Kew 2003. Published by Blackwell Publishing Ltd, 9600 Garsington Road, Oxford, OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA 7