title: ON THE LIFE HISTORY OF MONOSTROMA FUSCUM (POSTELS ET RUPRECHT) WITTROCK(1).
abstract: Results of the study of Monostroma fuscum from Son Juan Island, Washington, fully support the separation of the species M. fuscum from Monostroma sensu Wittrock into a taxon including M. obscurum. It would appear from this and previous studies that the M. obscunim-M. fuscum complex is clearly Ulvacean. The characteristics of the complex include (1) alternation of morphologically similar haploid and diploid generations; (2) production of biflagellate gametes and quadriflagellate zoospores; (3) a uniseriate form in early ontogeny; (4) thallus development progressing through a vesicular stage that, as a result of localized degenerative processes, opens at a size of less than I cm into a monostromatic blade; (5) cells elongated perpendicular to the plane of the thallus and with rotund-truncate ends: (6) a single elongate plastid, thickened at the opposite poles of the cell and thinner in the equatorial region of the cell; (7) a thallus composed of cells with relatively inelastic walls; and (8) discrete discharge pores. The chromosome number of Monostroma fuscum is n =9. The first division of the zoosporangium nucleus is meiosis I.
authors.affiliation: Department of Biology, Western Washington State College Bellingham, Washington 98225.
authors.forename: M A
authors.initials: MA
authors.lastname: Dube