Abstract
IN MOST haplobiontic green algae, the zygospores enter a dormant state which, often lasting for months, is broken only after a series of environmental changes that are fatal, in many instances, to the species in its vegetative state. The placoderm desmids are no exception. The rarity of observed sexual union in the desmids and the interval between zygo^pore formation and zygospore germination have resulted in a scarcity of published accounts of the latter. Inasmuch as the taxonomy of the desmids is based almost entirely on characteristics of the vegetative cells, few workers have concerned themselves with attempts to investigate sexual reproduction in the desmids beyond the chance observation of sexual union in natural collections and the even more rare observation of zygospore germination. The most complete accounts of zygospore germination in the placoderm desmids are those of DeBary (1858) who observed the entire life cycle of several species of Cosmarium, Closterium, and Staurastrum which he maintained in crude mixed culture in his laboratory. Periodic checks of these cultures during the period following zygospore formation resulted eventually in the observation of the germination process. Other workers have contributed to our knowledge of this phenomenon in these and other genera, such as Cosmariuam (Hofmeister, 1857; Klebahn, 1891), Closterium (Millardet, 1870; Klebahn, 1891; Morren, 1836), Staurastrum (Millardet, 1870; Turner, 1922), and Hyalotheca (Potthoff, 1927, 1928). Without exception, these reports have been based on chance collections or crude cultures. In an earlier paper, the writer (Starr, 1954a) reported the isolation of heterothallic strains of Cosmarium botrytis var. subtumidum Wittr. These strains are maintained in unialgal clonal culture and sexual union can be effected at will by mixing the two strains under appropriate environmental conditions. Inasmuch as these strains are being used in continuing cytological and genetic research in the writer's laboratory, it seems desirable to record for future reference the details of zygospore germination. The observations of DeBary (1858) on this process in Cosmarium botrytis are confirmed and expanded. The heterothallic strains of Cosmarium botrytis
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.