Taxonomic studies on the genus Ulothrix (Ulotrichales, Chlorophyceae). II

In this second report on the taxonomy of the Dutch species of Ulothrix Kutzing, the morphological and reproductive characters of three other freshwater species, viz. U. mucosa Thuret, U. crenulata (Kutzing) Kutzing and U. verrucosa Lokhorst (nom. nov.) are discussed. U. mucosa shows some relationship with Binuclearia tectorum (Kutzing) Beger ex Wichmann. These species are shown to differ in several respects, e.g. number of pyrenoids, morphology of the chloroplast, thickness of the H-pieces, morphology of basal and apical cells and structure of the zoosporangium cell wall. Close morphological resemblance exists between U. crenulata and U. verrucosa. Cell dimensions, morphology of the chloroplast and number of pyrenoids are the most important features for distinguishing these species. Both show taxonomic affinity to Klebsormidium Silva, Mattox & Blackwell. On account of chloroplast morphology, number of pyrenoids and shortening of cells the species are classified under Ulothrix. Under all photoperiods studied U. mucosa is the only species capable of reproduction by means of zoospores, whereas both other species referred to in this paper only show multiplication by fragmentation of filaments. Probably for this reason these species do not show seasonal periodicity in their occurrence in nature.