A Cytoplasmic Organelle associated with the Cell Walls of Chara and Nitella

Abstract

MATURE internodal cells of the algae Chara and Nitella are several centimetres long, and develop from meristematic cells about 20µ across. In an investigation of the fine structure of developing internodal cells in Chara and Nitella, an unusual organelle has been seen in the cytoplasm. In young internodal cells the organelle had a superficial resemblance to a mitochondrion, but a mitochondrion is always surrounded by a double membrane, whereas the organelle had a single outer membrane about 75 Å thick which resembled the ‘unit’ membrane of Robertson¹. In immature cells the organelle membrane appeared to be discontinuous on its cell-wall side, leaving small gaps through which there was contact between the inner structure of the organelle and the cell wall (Fig. 1). In developing cells the organelles were elongated in the direction of cell growth (Figs. 2 and 3) and the membrane surrounding the organelle appeared to be continuous with the cell membrane, of which it may be an extension.