THE PLANT CELL WALL has been investigated by a great number of workers with the intent of discovering not only the structure of the mature wall but the mechanisms of its formation as well. A chapter summarizing cell wall research is found in the work of Frey-Wyssling (1953). A complete analysis of wall formation will 1) relate changes in the fine structure of the wall with time, and 2) reveal how these changes, perhaps differing in rate or character in various parts of the wall, combine to mold the cell wall through successive configurations until the mature structure is attained. Fulfillment of the second objective requires a detailed description of the entire wall through time, preferably one made on a living cell. Castle (1937, 1942) marked growing sporangiophores of Phycomyces and from the movements of the marks was able to define the sub-apical zone and present interesting quantitative data concerning the kinetics of the spiral in that organism. The restriction of the complex processes to a small area has, however, made the details of wall formation in Phycomyces and tipgrowing cells (root hairs, pollen tubes, etc.) very difficult to discover, even with the penetrating techniques of X-ray diffraction and electron microscopy. Cells of growing higher plant tissues, as investigated by the electron microscoipe, appear to exhibit bipolar tip growth (Frey-Wyssling, 1953) but since the surface of these cells, when living, is inaccessible, studies of the manner and rates of surface extension can be made only by very indirect methods. The large cell walls of certain aquatic algae have been investigated with the electron microscope. Recently Steward and Miihlethaler (1935) presented a very extensive description of the developing cell wall of Valonia, fulfilling the first objective mentioned above. Growth appears to be distributed throughout the wall, but the origin of the shape of the Valonia cell, resembling a bottle with a rounded bottom, has not yet been quantitatively studied through time. This paper will present a surface study, through time, of the internode cells of the aquatic alga, Nitella axillaris Braun. These cell walls are particularly well suited for such a study because they are uniformly cylindrical and are accessible through a long period of growth. In the light of evidence that other members of the Characeae