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The ultrastructure of zoospores of Asterococcus superbus (Cienk.) Scherffel was studied to provide ultrastructural data relevant to the systematic position of the genus. Our results demonstrated that the motile cells of A. superbus were similar to those of the tetrasporalean algae, such as Tetraspora sp. and Tetrasporidium javanicum Moebius. The flagellar apparatus of A. superbus had the same clock-wise orientation of basal bodies and the V-shaped alignment of basal bodies as Tetraspora cylindrica (Wahlb.) Ag. and T. lubrica (Roth) Ag., but differed by having rhizoplasts. The motile cells of A. superbus displayed chlamydomonadal ultrastructure, similar to Chlamydomonas reinhardtii Dangeard, including the absolute configuration of the flagellar apparatus. The pyrenoid matrix in A. superbus, however, showed a large lateral invagination occupied by chloroplast stroma, a characteristic that has never been observed in Chlorophyta. [ABSTRACT FROM AUTHOR]

Vegetative cells and zoospores of Hormotilopsis gelatinosa Trainor & Bold, H. tetravacuolaris Arce & Bold, Planophila terrestris Groat,er & Hofstetter, and Phyllogloea fimbriata (Korchikov) Silva were examined by transmission electron microscopy. All cells had pyre-holds traversed by cytoplasmic channels. Zoospores were quadriflagellate and had essentially cruciate flagellar apparatuses. Scales were present on free-swimming zoospores. These features are essentially identical to those of Chaetopeltis sp. and are dissimilar to those of other described green algae. The new order Chaetopeltidales is created to accommodate the genera Chaetopeltis, Hormotilopsis, Planophila sensu Groover & Hofstetter, Phyllogloea, Dicranochaete, and Schizochlamys, organisms previously scattered among the orders Tetrasporales, Chlorococcales, Chlorosarcinales, and Chaetophorales. Members of the order are closely related to the ancestral chlorophycean flagellate genus Hafniomonas, may be ancestral with respect to other Chlorophyceae, and may also be closely related to the ulvophycean order Ulotrichale. [ABSTRACT FROM AUTHOR]

Cell wall structure and composition of fifty-one algae in the Volvocales, Tetrasporales, Tetrasporales, and Chlorosarcinales were investigated to determine the feasibility of using the presence of cellulose, wall fibers, and wall periodicity as taxonomic characters. Although members of the Volvocales consistently lack cellulose, the diversity of wall characters in the other orders discourages the use of these characters as taxonomic or phylogenetic criteria. [ABSTRACT FROM AUTHOR]

The unusual morphology of the coccoid, neustonic alga Nautococcus mammilatus Korschikov prompted its study with the electron microscope. Ultrastructural features including a fibrous cell wall with definite periodicity and an exgternal tomentum were observed. These and other features of the alga are compared with those of related species, and the use of cell wall characteristics in taxonomy is discussed. [ABSTRACT FROM AUTHOR]

The diagnostic characters alleged by Ettl (1981) and Ettl & Komarek (1982) to distinguish the Classes Chlamydophyceae and Chlorophyceae are discussed. The recognition of these classes ignores ultrastructural evidence of the close phylogenetic relationships of their members and produces an artificial redistribution of orders, families, and genera that can only lead to confusion in the taxonomy of the green algae. Suggestions for a more natural classification are made. [ABSTRACT FROM AUTHOR]