Certain Aspects of the Sexuality of Two Species of Chlamydomonas

SUMMARY. When older cultures (18 days old) of Chlamydomonas eugametos were mated, zygote formation occurred under conditions similar to those devised for C. moewusii. Young (6 days old) cultures of the former did not mate when the nitrogen concentration of the medium was high (0.03% NH₄NO₃). In confirmation of the work of Sager and Granick, it was found that low nitrogen concentrations, produced by decreasing the concentration of NH₄NO₃ in the original medium, by increasing the intensity of the illumination, or by using old cultures, enhanced gametogenesis in C. eugametos. It has also been demonstrated that the two species are compatible with one another, even under conditions which are unfavorable for gametogenesis in C. eugametos alone.