A New Rhadamanthus Species (Hyacinthaceae) from the Northwestern Cape, South Africa D. A. Snijman and John C. Manning Compton Herbarium, National Botanical Institute, Private Bag X7, Claremont 7735, South Africa PeterGoldblatt B. A. Krukoff Curator of African Botany, Missouri Botanical Garden, P.0. Box 299, St. Louis, Missouri 63166, U.S.A. Abstract. Rhadamanthus involutus is a rare, hysteranthous-leavedspeciesfromtheBokkeveld Escarpment,westofNieuwoudtville,NorthernCape Province, South Africa. Most closely related to R. alhiflorus B. Nordenstam, R. involutus is distin¬ guished by apically recurved outer tepals that are conspicuouslyspottedwithgreenatthebase,and suberect inner tepals that have involute margins which overlap to form a tube. The bulbs grow on exposedsandstonesheetsbetweenpatchesofdry fynbosandflowerinmidsummer. Rhadamanthus Salisbury is a small, poorly un¬ derstood genus of Hyacinthaceae that is endemic to southern Africa. Nordenstam (1970) and Ober- meyer (1980) recognized 11 species, mostly from semi-arid habitats in the Nama Karoo, Succulent Karoo, and Fynbos biomes (see Rutherford. f997). The genus is distinguished from its close ally, Ur- ginea Steinheil, solely by its derived anther dehis¬ cence.Unliketheunspecialized,longitudinallyde¬ hiscent anthers of Urginea, the anthers in Rhadamanthusdehisceeitherapically,orifbylon¬ gitudinalslitsthentheseareinitiatedfromtheapex and extend below the midline but never reach the base of the thecae. Despite this variation, dehis¬ cenceinRhadamanthusisnevercompleteandthe antheropeningalwaysremainssomewhatpore-like, havingitsgreatestwidthnearthetopoftheanther (Nordenstam,1970).Althoughsubtle,Nordenstam (1970) chose to maintain this distinction, awaiting theresolutionofthedifficultandcomplexrelation¬ ships between the remaining genera in tribe Scil- leae (sensu Hutchinson, 1959). Jessop (1977) sup¬ ported this view in his re-evaluation of Drimia JacquinexWilldenow,Urginea,andrelatedgenera. PlantsofRhadamanthusareeasilyoverlookedin thefield.Theleavesareconsistentlyhysteranthous, theflowersareinconspicuous,andthebulbsflower duringtheunfavorablesummerdrought.Thusthe geographicrecordsofmanyRhadamanthusspecies inNordenstam’s(1970)treatmentofthegenusare regarded as incomplete, and the fruit and seeds of severalspeciesstillremainunknown. Rhadamanthusinvolutuswasfirstdiscoveredin 1993 in flower in sparse, dry fynbos on the Bok¬ keveldEscarpmentwestofNieuwoudtville,north¬ western Cape. The flowers differ uniquely in the form, disposition, and markings of the outer and inner tepals. The tepals are unequal and biseriate, with the outer whorl distinctly overlapping the in¬ nerwhorlatthebase.Theoutertepalsrecurveapi¬ callyatanthesisandeachbearsadistinctive,basal, olive green spot. In contrast the inner tepals are unmarked,suberect,andinvolutesothateachhas ataperingtubularform.Thenon-noddingflowers are also unusual in the genus. Anther dehiscence in R. involutus is tardy and incomplete, and the longitudinal slits which proceed from the apex of the thecae do not extend to the base. Obermeyer (1980)recognizedfourotherspeciesofRhadaman¬ thus (R. fasciatus B. Nordenstam, R. alhiflorus B. Nordenstam,R.namibensisObermeyer,andR.ka- rooicusObermeyer)withthistypeofantherdehis¬ cenceanddescribedsubgenusRhadamanthopsis Obermeyertoaccommodatethem.Rhadamanthus involutus is the fifth known species of this subge¬ nus.Althoughitsaffinitiesinthegenusarenotwell understood,R.involutushaswhiteflowersandex¬ tremely short filaments relative to the anthers. These characters also occur in R. alhiflorus and suggest an alliance with this southwestern Cape species. Field observations on the bees (family Antho- phoridae) that visit the flowers of R. involutus in¬ dicatethattheantherdehiscenceinRhadamanthus isassociatedwithpollinationbybeevibration.Ad¬ ditional characters that Rhadamanthus species share with other known buzz-pollinated taxa (Er- Novon 9: 111-113. 1999.