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).