3.2. Umbellet development
The center of all umbellets dome-shaped at early stages (Fig. 3c-d, Fig. 4a). In peripheral ones, floral primordia initiated in unidirectional order, starting from abaxial. Numerous primordia, first, arise at abaxial side, followed by inner ones at the adaxial side. Then, the rest ones initiated on lateral sides (Fig. 3c). In inner umbellets, in contrast, floral primordia initiated as modified helical sequence (Figs. 3d, 4a).
In each umbellet, two rings of floral primordia initiated that centered on a large primordium. Primordia are sessile, round-shaped and unequal. Peripheral ring primordia are larger than inner one. The central one, however, is the largest (Fig. 4b). Pedicels of the peripheral flowers grow fast, followed by elongation of its floral organs. Afterward, the perfect flower starts to expansion at opposite sides (Fig. 4c). The initiation of its floral organs is simultaneous with those in inner staminate flowers (Fig. 4d-e). In cage like umbellet, the inner ring of staminate flowers are obviously smaller than peripheral ones. Both rings centered on a thick hairy fruit (Fig. 4f).