Observations with the electron microscope on Asteromonas gracilis Artari emend. (Stephanoptera gracilis (Artari) wisl.), with some comparative observations on Dunaliella Sp

A clone of Asteromonas gracilis has been examined in culture by means of light and electron microscopy. The morphological observations of Artari (1913) have been confirmed and extended. New observations include demonstration of an unusual type of pyrenoid somewhat resembling that of Prasinocladus, with tubular channels entering the pyrenoid centre from outside the plastid and penetrated by haustorial outgrowths from the nuclear envelope. The very different structure characteristic of Dunaliella is briefly illustrated. Other comparisons indicate that A. gracilis is the type species and sole known representative of a very distinct genus which cannot be confused with Pyramimonas and is unlikely to be synonymous with the imperfectly known genus, Stephanoptera.