The Life History of Prasinocladus ascus as Found in Japan, with Special Reference to the Systematic Position of the Genus

Prasinocladus ascus in the region of Shimoda, Japan, exists only as asexually reproducing plants. The plants grow only in winter. They survive during unfavorable periods as thick-walled cysts, which are capable of rejuvenation and normal development with the return of favorable conditions. The zooids have a depression at the anterior part, in which the flagella are inserted. The flagella of the zooids are of the “tinsel type”. The cell walls of P. ascus seem to lack cellulose. From these observations, it is suggested that Prasinocladus is not a member of the tetrasporine alliance, but a derivative of Platymonas. It might also be suggested that there is a need for further study to ascertain whether Prasinocladus is a member of the Chlorophyceae.