Developmental stages of male flowers. A. Initiation of stamens (asterisks) at the periphery of the floral primordium. Scale bars = 75 μm. B. Later stage of development of stamens (asterisks). Scale bars = 150 μm. C. Early stage of formation of synandria by the concrescence of stamen primordia (asterisks). Scale bar = 125 μm. D. Stage at which synandrium becomes a unit. Arrows, depression at the center of the synandrium. Scale bar = 150 μm. E. Nearly mature synandria with depression (arrow) still visible. Scale bar = 250 μm. F. Higher magnification of mature synandria. The central depression (arrow) remains visible on some flowers. Scale bar = 150 μm.