Reproductive cycles of Calocedrus formosana

Vegetative shoots of Calocedrus formosana continually initiated leaves and lateral branches from early March until the end of October. Pollen cones were initiated on proximal vegetative shoots from mid-June to early July, and development continued until the end of September. Seed cones were initiated on newly formed, distal axillary vegetative shoots from late June to mid-July. Transition to a seed-cone apex was marked by an increase in mitotic activity followed by bract-scale initiation. Usually 2 ovules were initiated in the axil of each bract scale. Pollen cones and seed cones ended dormancy in early February, microsporogenesis occurred in mid-February, and pollination occurred in late February. Pollination occurred during a 2-wk period. Pollination drops were exuded from 4 ovules at one time. Pollen contacting the pollination drop was rapidly taken in. Pollen frequently germinated and elongated in the pollination drop within the micropyle before reaching the nucellus. The pollination drop was withdrawn into the micropyle which was later sealed by enlargement of the cells lining the micropylar canal. Pollen tubes penetrated most of the nucellus during late May, then pollen-tube growth slowed until early June when the pollen tubes quickly extended to the surface of the neck cells. Mega-sporogenesis occurred in late February, but female gametophytes did not mature and fertilization did not occur until late May. An archegonial complex formed containing 4~6 archegonia, of which several were usually fertilized. Proembryo development varied depending upon the size and shape of the archegonia. Cleavage polyembryony was observed in this plant. Embryos had matured by mid-August, and most seeds were shed in September and October. The potential seed set was only 4 seeds per cone and filled seeds averaged only 1 or 2 per cone.