Floral Morphology, Embryology, and Seed Anatomy of Ruptiliocarpon caracolito (Lepidobotryaceae) Hiroshi TobeDepartment of Biology, College of Liberal Arts and Sciences, Kyoto University, Kyoto 606, Japan Barry E. Hammel Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166, U.S.A.ABSTRACT. Floral and seed anatomy of Ruptilio-carpon caracolito, based on histological studies, aredescribed in detail. Cryptic dioecy, a nectariferousstaminal tube, and ovules with obturators comprisethe characters most crucial to elucidation of rela-tionships of this taxon. Originally compared amongSapindales, Ruptiliocarpon seemed close to but dis-tinct from Meliaceae; floral anatomy suggested thatit be recognized in its own separate family, a moveobviated by the discovery of its close relationship tothe monotypic African Lepidobotryaceae. However,the floral and seed anatomy of Lepidobotrys havenot been studied in the same detail as those ofRuptiliocarpon, and the relationships of Lepido-botryaceae (Ruptiliocarpon and Lepidobotrrys) re-main controversial. A preliminary survey of theliterature supports the suggestion that Lepidobotry-aceae may be closer to Sapindales or perhaps Eu-phorbiaceae than to other groups with which it hasbeen compared. Histological studies of floral and seed anatomyoften provide critical information for discoveringrelationships of problematic taxa (cf. Tobe, 1991;Hammel & Wilder, 1989). Material from collectionsof yet another Costa Rican tree that could not beplaced to family was analyzed to that end.MATERIALS AND METHODS Buds (Aguilar & Hammel 101, Aguilar et al.103, Hammel et al. 18154, 18166), young fruitsand mature seeds (Aguilar et al. 103, Hammel17983) were fixed in FAA for this analysis. Budsand young fruits were softened as described in Tobe& Raven (1984) and thin sectioned with a rotarymicrotome following standard paraffin methods. Sec-tions were stained with Heidenhain's hematoxylin,safranin, and fastgreen FCF. Pieces of mature seedcoat were dehydrated through an ethanol series,embedded with Technovit 7100 (Kulzer & Co., Ger-many) resin, sectioned on a rotary microtome andstained with 0.02% Toluidineblue O (Tobe et al.,1992).FLORAL MORPHOLOGY As indicated by anatomical sections, flowers areunisexual and the plants apparently dioecious. Allflowers have stamens and a pistil, but the pistil ofmale flowers (Aguilar & Hammel 101, Hammel etal. 18154, 18166) is smaller than that of femaleflowers (Aguilar et al. 103) and bears only rudi-mentary ovules (Figs. 1, 2). Female flowers havestamens with shorter filaments and lack pollen grainsin anthers (Figs. 4, 5). Flowers are pentamerous, comprising five sepals,five petals, ten stamens, and one pistil (Figs. 2, 4,7). Both sepals and petals are free and imbricate inaestivation and alternately arranged. The ten sta-mens are inserted at the same level of the receptacleand fused along nearly the entire length of theirfilaments, forming a staminal tube (Fig. 2). Thestaminal tube is particularly conspicuous in the maleflowers, where filaments are longer. There, the fiveantisepal stamens have a short length of free filamentextending beyond the staminal tube, while the fiveantipetal stamens lack free filament (Fig. 7A, H, J).In the male flowers the nectariferous staminal tubeis densely stained and even has vascular tissue thatis profusely branched on the adaxial side (Fig. 3).The staminal tube is massive and histologically ap-pears to represent a nectary. Neither an intrastam-inal nor a gynophoreal nectary is present. In femaleflowers, however, the staminal tube is less conspic-uous (Fig. 6) and may not actually exude nectar. Vascular tissue just below the level of the recep-tacle in male flowers forms a vascular cylinder ofca. 10 discrete vascular bundles (Fig. 7B). At andabove the level of the calyx, the vascular bundlesdivide and successively supply vascular tissue tosepals, petals, stamens, and pistil (Fig. 7C F). Each NOVON 3: 423-428. 1993.
BioStor
