The Fine Structure of Vesicles Associated With the Cell Surface in Helianthus Shoot Tissue

The fine structure of vesicles which were observed in association with the cell surface of shoot tissue of Helianthus annuus is described. These unit membrane-bound vesicles, which were up to 2 μ in diameter, contained tubules and occurred in several tissues of the shoot. They were present deep within the cytoplasm, as well as in close association with the cell wall, where they fused with the plasmalemma and appeared to empty their contents in the vicinity of the wall. These vesicles are compared to similar structures described by other investigators. The possible relationship of these structures to deposition of cell wall materials is discussed.