Cronología reproductora de Ceratozamia mexicana (Cycadales)

In Ceratowmia mexicana Brongn. seed development is completed in 24 months from the initiation of ovules in August until the full development of the body of the embryo. Megasporogenesis and megagametophytogenesis occur during the first three months. At the end of February the gametophyte is coenocytic. Cellularization of the gametophyte ends in May, when other changes begin: hardening of the gametophyte, lignification of the stony layer, disappearance of trichomes, and accumulation of starch in the gametophyte. Pollination probably occurs in February and March. By the beginning of September, proteins and oil droplets appear in the gametophyte. Seeds are dispersed in September, at which time arquegonia may be present and occasionally developing suspensors. Fertilization occurs approximately at the time of dispersal, separately from the mother plant. Suspensors grow during five months and the body of the embryo develops during four months. Thus, development of protection and storage of nutrients precede the formation of the embryo.