The Structure and Development of the Cell-Wall in the Valoniaceae as Revealed by the Electron Microscope

Abstract

The cell walls of Valonia ventricosa, V. macrophysa, V. ocellata, and Dictyosphaeria favulosa have been investigated with the electron microscope. The pattern of wall structure and development appears to be similar in all. The firat wall consists of a tangle of cellulose fibrils embedded in amorphous material, possibly pectin. Later, cellulose is laid down in successive larnellae in which the fibril direction shifts abruptly from layer to layer apparently through 120°, so that the direction is repeated on every fourth layer. During cell-extension, tearing of the lamellae occurs. The implication of the observed facts is discussed.