3.1. Umbel and club-like organ development
The umbel meristem naked and disc-shaped (~100 μm
diameter) at early stages. It fractionates centripetally numerous
umbellets and involurcal bracts (Fig. 3a). The center of the umbel
remains flat and undifferentiated throughout entire development except
last stages. Rarely, the center fractionates the small segments. The
peripheral umbellets enlarged fast, which become semi-spherical and
unequal (Fig. 3b). The umbellets fractionate floral meristems, followed
by incurving towards center of the umbel (Fig. 3c). The center remains
flat and naked even after fractionation of inner umbellets into floral
meristems (Fig. 3d). It starts to bulge along with fractionation of
floral organs. The small bulb-like head with short column, first,
initiated. The head restricted by massive floral meristems whose rays
and pedicels not enlarged. From side view, it is still not visible due
to overtopping by peripheral umbellets (Fig. 3e). Then, its column
enlarged along with growing rays of the inner umbellets (Fig. 3f). It
grows fast, becomes club-shaped, stands at the umbel center and overtops
the umbel plane (Figs. 3g).
The surface of the head is smooth, reticulate and vermiculate with
lumens (Fig. 3h). The column is striate and covered by a few small (Fig.
3i) or massive sessile glands (Fig. 3j).