THE FINE STRUCTURE OF A PERITAPETAL MEMBRANE INVESTING THE MICROSPORANGIUM OF <i>PINUS BANKSIANA</i>

Abstract

S ummary An acetolysis‐resistant membrane develops around the microsporangium of Pinus banksiana while the pollen mother cells are undergoing meiosis. The formation of this membrane appears to involve the deposition and polymerization of sporopollenin precursors upon a primary layer believed to be lipid. The source of both these components is considered to be the tapetum and attention is drawn to the similarity in construction between this membrane and the tapetal orbicules. Possible functions of the membrane in the development and dispersal of the pollen are discussed.