Embryogeny of Carya and Juglans, a Comparative Study

Abstract

Embryo sac features, pollination, derivation and development of endosperm were studied in C. glabra and J. mandshurica, with particular attention to embryogeny, especially in its later phases, including origin of cotyledons, primary root, and plumular bud, with the morphology of the growing points of root and shoot axis. Approximately 350 fixations were prepared through 2 collecting seasons (Apr.-Aug., 1931 and 1932). Collections were made 3-4 times weekly to the time of pollination (May 6-10 in Juglans, May 12-15 in Carya), after pollination daily for 2 weeks; and then at intervals of 2-3 days through June, July, and early Aug. (periods of embryo and fruit development). No significant differences were found between Carya and Juglans in the history of the megasporocyte, megaspores, and embryo sac, other than a marked contrast in the sizes of their gametophytes, and a more definitely organized condition of the micropylar apparatus in Carya; also a noticeable shortening of the period of megasporogenesis and the intervals from pollination to fertilization, to 1st division of the zygote in J. mandshurica as compared with C. glabra. In both, the definitive nucleus divides before the zygote, a parietal layer of endosperm with numerous free nuclei being one of the distinctive features of the enlarged embryo sac prior to division of the zygote. Stages in proembryonic and later embryonic development are described both for Carya and Juglans, but generalizations are deferred until the completion of studies in progress relating to the embryogeny of the Juglandaceae and Fagaceae.