Sequencing of cDNA Clones and Analysis of the Expressed Sequenced Tags(ESTs)Properties of Male Floral Buds of Populus deltoides Construction of Full-length cDNA Library of MaleFloral Buds of Popu lus de ltoides Hormonal Control of Sex Differentiation of Potentially Female Floral Buds of Lagenaria siceraria var. hispida In Vitro