La Structure Fine de Chlorogonium elongatum. I. Etude Systematique au Microscope Electronique.

The flagellate Chlorogonium elongatum has been studied in the electron microscope by thin-sectioning techniques. The nucleus, limited by a porous membrane, contains a large nucleolus and some dense masses, probably of chromatin. When the medium is rich or the culture young, the chloroplast has few lamellae, and very few pyrenoids. Inversely, when the medium is poor or jthe culture old, the lamellae are abundant, appearing as piled discs or as a tortuous lamellar system. The pyrenoids are then numerous and are surrounded by starch grains. They are composed of an opaque, finely granular substance, and are never traversed by chloroplast lamellae. The stigma, within the chloroplast, is a circular or oval plate composed of a single tier of dense granulations. The cytoplasm contains mitochondria which are concentrated near the pellicle of the cell, an endoplasmic reticulum, an abundance of ribo-nucleoprotein particles or ribosomes, and a Golgi apparatus. These organelles resemble those observed in other protozoa. The two fiagella are encased in cylinders situated at the anterior end of the cell. At the base of the fiagella are the basal corpuscles or kinetosomes, which repose within a cupule. A dense granule which probably corresponds to the centrosome appears near this structure.