FLORAL ANATOMY IN THE SAXIFRAGACEAE SENSU LATO. III. KIRENGESHOMOIDEAE, HYDRANGEOIDEAE AND ESCALLONIOIDEAE

Abstract

The floral morphology and anatomy of the one species in the monotypic Kirengeshomoideae, eight species in the Hydrangeoideae, and six in the Escallonioideae are described and compared. Similarities in floral structure and vascularization between Kirengeshoma palmata and members of the Philadelpheae strongly support the placement of this genus in the same subfamily as the tribe—the Hydrangeoideae. While the anatomy and morphology of flowers in the Hydrangeoideae do not clearly exclude the subfamily from a family that also includes the Saxifragoideae, certain commonly appearing floral characteristics probably do. These include relatively extensive polyandry, the frequent occurrence of highly vascularized isomerous gynoecia, petals with lateral bundles originating from traces in the sepal planes, no suggestion of a floral cup continuing beyond the divergence of the floral organs from the carpel walls in epigynous flowers, and essentially no independence among carpels in the ovary region of the gynoecium. In addition, a fascicled stamen arrangement characterizes the polyandrous members (Philadelpheae mostly). Although floral anatomy of too few members of the Escallonioideae has been investigated, the floral characteristics of this subfamily appear to be very diverse and not particularly distinctive when compared with the Saxifragoideae. Some diagnostic trends may be recognized, however: Escallonioids generally have fewer ovules per carpel (except Escallonia), less commonly show independence between carpels, and have epidermal hairs that are quite different from the complex trichomes of the flowers in Saxifragoideae. In addition, the ventral carpel bundles in two species studied in the subfamily terminate at the top of the ovary and do not enter the style.