The morphology of the wet, non-papillate (WN) stigma form in the tribe Caesalpinieae (Gaesalpinioideae: Leguminosae)

Stigmas in 24 species of 11 genera, classified in three groups, Caesalpinia, Peltophorum and Dimorphandra, of the tribe Caesalpinieae have been examined by light and scanning electron microscopy. All are of the WN (wet, non-papillate) form. The receptive stigmatic surface comprises a crater, generally at the apex of the style, which in fresh flowers is full of clear fluid. The crater rim may be fringed with non-receptive hairs, and its shape and depth are variable between species. Extreme forms are found in Caesalpinia sappan where crater hairs are short and the crater funnel-shaped and very deep, and C. vesicaria and Delonix regia where crater hairs are long and the crater appears very shallow.