The significance of floral features within infrageneric classification of Euonymus (Celastraceae)

Euonymus is a highly diverse and cosmopolitan genus within Celastraceae. Floral anatomy of twenty-eight Euonymus taxa were investigated to examine whether floral features provide useful information for infrageneric classification using light microscopy and scanning electron microscopy. The floral characters were evaluated by cluster and principal coordinate analysis. Flower merosity, petal color, and ovule number per locule were of potential systematic value as supported by ordination analysis. In addition, morphological data on the ovary of Euonymus were first reported here, and three subtypes of axile placentation were detected: (1) apical-axile, (2) basal-axile, and (3) dispersed-axile. This study highlights the importance of the floral features and provides better understanding of the relationships among sections in Euonymus.