The ontogenetic basis for missing petals in Crudia (Leguminosae: Caesalpinioideae: Detarieae)

Crudia choussyana (in Crudia group of Cowan and Polhill) has a relatively simple, radially symmetrical flower structure but is unusual among legumes in lacking petals. Floral initiation and development were examined using scanning electron microscopy. Significant ontogenetic features include a circular, prepetal-initiation floral apex and the abaxial, nonmedian position of the first sepal initiated. Five petals are initiated, but the primordia fail to enlarge and disappear completely by midstage, well before anthesis. The 10 stamens are in two alternating whorls and are initiated unidirectionally from the abaxial side. The carpel is initiated concurrently with the petal primordia. Absence of petals can occur by several developmental pathways among legumes.