An Alternative Mode of Elimination of Resin from Epithelial Cells of Resin Ducts in Pinus sylvestris Cytochemical Localization of Pectinase: the Cytochemical Evidence for Resin Ducts Formed by Schizogeny in Pinus massoniana THE STRUCTURE, DISTRIBUTION AND DEVELOPMENT OF THE RESIN DUCTS IN THE SECONDARY STRUCTURE OF STEM OF PINUS TABULAEFORMIS CARR THE INITIATION AND DEVELOPMENT OF RESIN DUCTS IN PINUS TABULAEFORMIS CARR Initiation and Development of Resin Ducts in Major Organs of Pinus massoniana Development and Histochemistry of Resin Ducts of Secondary Xylem in the Stem of Pinus tabulaeformis Carr. HISTOCHEMISTY OF RESIN DUCT DEVELOPMENT OF PINUS TABUL AEFORMIS CARR