Dr. Usher Posluszny

Dr. Usher Posluszny
Professor Emeritus
Department of Molecular and Cellular Biology
SCIE 4447


  • B.Sc. McGill University
  • Ph.D. McGill University


The work in my lab concentrates on comparative morphology and development as related to the systematics and evolution of two large and important groups: 1. aquatic monocotyledons (Alismatidae) and 2. the grape family (Vitaceae). A particular focus has been the development of flowers that has allowed us to consider the functional questions related to reproductive biology. This work and the varied techniques used in my lab has been recognized as quite unique...certainly within the Canadian botanical community.

Some of the ongoing work in my Plant Morphology Lab is described briefly below.

  1. The Botany of Seagrasses. (in collaboration with Dr. P. B. Tomlinson, Harvard University and Dr. Paul Cox, National Tropical Botanical Garden, Hawaii) This is a long-term project that will culminate in a comprehensive monograph on the morphology,anatomy and reproductive biology of marine monocots.
  2. A Comparative and developmental study of the Vitaceae. (in collaboration with Dr. Jean Gerrath, University of Northern Iowa) The family Vitaceae is primarily known for the commercial wine and table grapes but there has never been a complete and comprehensive study done of this large and important family of temperate and tropical lianas.

Selected Publications

Book Chapters and Reviews

  • Posluszny, U., W. A. Charlton, and D. H. Lex. 2000. Modularity in Helobial flowers. Monocots: Systematics and Evolution. Eds. K. L. Wilson and D. A. Morrison. (CSIRO: Melbourne).
    • This paper proposes a mechanism for evolution in the aquatic Monocotyledons. Several processes including modularity and sterilized inflorescences are discussed.

Research Papers

  • Gerrath, Jean M., T. Wilson and Usher Posluszny. 2004. Morphological and anatomical development in the Vitaceae VII. Rhoicissus digitata. Can. J. Bot. (In Press).
    • Rhoicissus digitata is a member of the vitaceae that has been used for decades as a horticultural houseplant. It's native to southern Africa and has been a key species in our series on the vitaceae providing crucial information on vegetative and floral development in the family and clues as to the relationships with presumptive sister groups.
  • Posluszny, U. and P. Barry Tomlinson. 2003. Aspects of inflorescence and floral development in the putative basal angiosperm Amborella trichopoda (Amborellaceae). Can. J. Bot. 81: 28-39.
    • This paper looks at one of the most controversial plants today, believed to be the basal most angiosperm extant...the plant from which all other angiosperms have originated. This study is the first fully developmental study done on the flower and inflorescence of this very important species.
  • Wilson, Trevor and Usher Posluszny. 2003. Complex tendril branching in two species of Parthenocissus: Implications for the vitaceous shoot. Can. J. Bot.: 81: 587-597.
    • The architecture of the vitaceous shoot is still poorly understood. This study provides an insight into the development of the tendril in Parthenocissus which is the most comprehensive study of this structure ever undertaken and has clarified the architecture of the tendril.
  • Wilson, Trevor and Usher Posluszny. 2003. Novel variation in the floral development of two species of Parthenocissus. Can. J. Bot 81: 738-748.
    • This is the first study of the comparative floral development in two species of Parthenocissus and has provided novel insights in to the complexity of floral development in the vitaceae.