Wall developments and coordinated cytoplasmic changes in spermatogenous cells of Polytrichum (Musci)

In a growing antheridium of Polytrichum, walls of the androgonial cells are conventional, except for frequent interruptions due to protoplasmic connections, which are larger than plasmadesmata, between adjacent androgones. Prior to final division, protoplasts round up because of thickening of the walls at the corners of cells. Dictyosomes seem to be important in secretion of wall materials. After the last division the thick walls take on a reticulate, and then alveolar, appearance in sectional views as the walls become the intercellular matrix. Each of the developing androcytes deposits a uniform granular wall layer against the alveolar matrix. The granular layer becomes the vesicle in which a sperm is released. In addition, an irregular granular-fibrillar layer is deposited within the vesicle. At maturity numerous sperm vesicles of a sperm mass are embedded in a continuous phase of lipid droplets. Lipids replace the thick walls that were present when androcytes were first differentiated. Wall developments are part of the preparation of the sperms for dispersal, and, as such, they are a crucial aspect of sperm maturation.