Unicellular alga symbiotic located in hospite within hosts’ endodermal cells as coccoid cells that divide in the coccoid state, as they do in culture. In the hosts, the algal cells are 11-13 pm in diameter, in culture 11-1 5 pm. Cells in culture are palmelloid, with one to four cells in a mucilaginous matrix. Nucleus with approximately 30 large chromosomes, limited by an envelope comprised of two membranes with pores. Chloroplast envelope comprised of three membranes; thylakoids in groups of three; two pyrenoids with invasive chloroplast thylakoids. “Accumulation body” present in host and in culture. No trichocysts observed. Dinomastigote stage not studied in detail.