Abstract
The fine structure of the internodal cells of G. australis in the linear phase of cell expansion is described from electron micrographs of thin sections of osmium. and permanganate-fixed material. . The static picture obtained is basically similar to that of the parenchyma cells of higher plants as established by electron-microscope observations. A unit volume of protoplast has the same fine structure in cells ranging from 1 em to many centimetres in length, and contains cell wall, plasmalemma, tonoplast, endoplasmic reticulum, golgi bodies, micro somes, mitochondria, chloro_ plasts, nuclei, and other inclusions. This constant structure may account for the constant metabolism per unit volume of protoplast during the linear phase of development. A brief discussion of the possible significance of this picture of the structure of the internodal protoplast to the functional activity of the cell is given.