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. Cell walls and associated space around a protoplast are thought to be greatly affected by activities of various components of the protoplast. For example, dictyosomes are in a state of rapid turnover in some plant cells, which exhibit a flow of membranes and secretions, via vesicles, to the plasma membrane, the cell wall and the extra-cellular space (Morr6 & Mollenhauer, 1974). Multivesicular bodies (Schulz & Lehmann, 1970) and various types of paramural bodies (Berlyn, 1970) also appear to be involved in addition of materials to cell walls. This paper correlates protoplasmic changes with the changing nature of the walls and associated spaces around each spermatogenous cell during spermatogenesis in the moss Polytrichum. Changes in the walls are also evaluated in terms of their significance for dispersal of the sperms at maturity. The sequence of protoplasmic events leading to maturation of sperms was described elsewhere (Paolillo et al., 1968a,b). MATERIALS AND METHODS Polytrichum juniperinum Hedw., collected at Portland Arch, Indiana, was used for this study. Methods used include conventional gluteraldehyde fixation, Epon embedding and thin 1 Supported in part by National Science Foundation Grant GB-25097. 2 Section of Genetics, Development and Physiology, Cornell University, Ithaca, New York 14853. SPresent address: College of Veterinary Medicine, Cornell University, Ithaca, New York 14853. This content downloaded from 157.55.39.96 on Mon, 18 Apr 2016 08:29:18 UTC All use subject to http://about.jstor.org/terms 1976] PAOLILLO & CUKIERSKI: SPERMATOGENESIS IN POLYTRICHUM 467 sectioning (Paolillo et al., 1968a,b). Additional observations were made with a Phillips 300 microscope and an improved staining technique, in which 5% methanolic uranyl acetate was applied for 30-40 min. in a covered dish in a cool room (160C) to minimize evaporation. This was followed by lead citrate. Using this procedure, greater contrast and fewer precipitates were obtained than with shorter applications of 25% methanolic uranyl acetate (Stempak & Ward, 1964) at room temperature, followed by lead citrate. Terminology applied to stages of development is according to Allen (1912).