Several years ago the author has proposed a theory to explain the microfibrillar texture observed electronmicroscopically in primary cell walls of growing tubular cells (Houwink and Roelofsen, 1954; Roelofsen 1950, 1951; Roelofsen and Houwink 1951, 1953). It was called multinet growth. This theory supposed that the major part of new microfibrils is continuously deposited transversely on the inside of the wall. As growth proceeds, the unidirectional extension of the wall causes a reorientation of the texture, first into a crossed fibrillar or random structure, finally into a more nearly longitudinal texture. This progressive reorientation does not occur in the inner layer but only in those layers which are displaced outward by the cell wall deposition on the inside. This will ultimately result in a longitudinal arrangement on the outside while the freshly deposited inner side continuously exhibits a more or less transverse orientation. It was also pointed out that such reorientation cannot occur in the whole primary cell wall but only in certain layers of it. The theory was postulated especially for cells or parts of cells exposed to the atmosphere, viz. plant hairs, fungal hypha and aerenchyma cells.