Morphology and Anatomy of the Flower and Pollen of Saruma henryi Oliv., a Phylogenetic Relict of the Aristolochiaceae

Abstract

DIcIusON, W. C. (Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280). Morphology and anatomy of the flower and pollen of Saruma henryi Oliv., a phylogenetic relict of the Aristolochiaceae. Bull. Torrey Bot. Club 119: 392-400. 1992.-A study of the floral morphology and anatomy and pollen morphology of the monotypic Chinese genus Saruma was undertaken to provide a more thorough diagnosis of the plant and make comparisons with other members of the Aristolochiaceae. The possession of well-developed petals, a gynoecium of partially separate carpels, follicular fruit, and a monosulcate form of pollen document the primitive position of the genus. Pollen is semitectate and reticulate with a stratified, columellate wall structure. The gynoecium is of particular phylogenetic interest and is composed of a primitive form of three-trace carpel with an elongated, pubescent stigmatic region that extends along the exposed ventral (adaxial) surface. Numerous ovules are borne in two longitudinally oriented, submarginal rows and are vascularized by traces arising from the ventral bundles. The pattern of floral vascularization is similar to other members of the Aristolochiaceae, exhibiting the tendency for extensive fusion of vascular bundles. Unlike other Aristolochiaceae, oil cells and calcium oxalate crystals are absent from floral tissues. Saruma also diverges from the Aristolochiaceae by possessing stamens that become recurved inward at maturity, creating a functionally introrse dehiscence. Reproductive morphology provides compelling evidences for the segregation of Saruma to a distinct subfamily within the Aristolochiaceae. There is little convincing evidence to indicate that Saruma and Asarum share a common ancestry.