The fine structure of the pit connections ofBatrachospermum sirodotii skuja

Abstract

A new type of pit connection is described in the fresh water red algaBatrachospermum sirodotii and reported inTuomeya sp. consisting of a doughnut-shaped pit ring with a central pore that is occluded by a rivet-shaped pit plug. This structure occurs in pit connections between cells of the indeterminant axes and also cells of whorled assimilatory branches of limited growth, the pleuridia, but not between axial cells and the basal cells of the pleuridia, the periaxial cells. The pit plug and pit ring ultimately break down in pit connections of the main axis reopening the septal pore to intercellular cytoplasmic connection between vegetative axial cells. A similar breakdown of pit connections may also occur in the pleuridia. The functioning of a truncated cone-shaped network of endoplasmic reticulum in the development of the pit connection is described.