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Abstract
This paper∗ deals with a new type of green alga originally found on the Cape Flats and since obtained in the United States of America and Australia. Initially identified as a second species of Volvulina Playfair, the considerations which led to the establishment of a distinct genus, Astrephomene, including the appearance from the Flats of Volvulina itself, are summarized, Playfair's description analysed and the resultant conclusion that he was dealing with two different algae mentioned; the steps that resulted in the verification of this conclusion are indicated. The two methods of culture used in the investigation are described.
An amended description of Volvulina steinii Playfair is given and the results of observations made during a study of the alga in culture are recorded.
The genus Astrephomene with the single species A. gubernaculifera is defined, a full account of its structure and life history given and its similarity to and difference from Volvulina pointed out, particularly the absence of inversion and the possession of a unique directive organ, the ‘rudder’.
The results of cultures selected to illustrate certain points are summarized and the value of soil cultures in the study of algae emphasized.
The validity of Playfair's genus is discussed, references by Stein and Carter are analysed and the possibility of its occurrence in India suggested. The relation between nutrition and certain features common to both algae is discussed, the characters of the two compared and the taxonomic position of each considered. A new family of the Volvocales, astrephomenaceae, is proposed for the reception of the monotypic genus, Astrephomene.
