Cytology of Differentiating Tracheary Elements. II. Structures Associated with Cell Surfaces

During the differentiation of helical secondary walls in tracheary elements of Beta vulgaris L. and Cucurbita maxima Duchesne special structures were recognized on both sides of the plasmalemma in variously fixed material. Microtubules oriented parallel with the expected orientation of microfibrils in the cell wall occur near the inner side of the plasmalemma. Inclusions in the form of vesicles and tubules occur between the plasmalemma and the wall in pockets apparently formed by invaginations or infoldings of the plasmalemma into the cell interior. The concepts on possible relation of these structures to the growth of the wall are reviewed.