Phylogenetic analyses, based upon nuclear small-subunit ribosomal RNA gene sequences, of four ‘chlorosarcinoid’ species referred to Planophila Gerneck show that the genus is polyphyletic. The type species, P. laetevirens Gerneck, is closely related to species in the Ulotrichales, Ulvophyceae. The monotypic sarcinoid genus Pseudendocloniopsis is the closest relative of Planophila; the two genera represent the addition of a new morphological type to the Ulotrichales. Planophila microcystis (Dangeard) Kornmann & Sahling forms a clade at the base of the Ulvophyceae with Oltmannsiellopsis, and thus belongs to the Oltmannsiellopsidales. This result is also supported by the Oltmannsiellopsis-like ultrastructure of P. microcystis zoospores. Planophila sp. B from Antarctica, which has Trebouxia-like pyrenoid structure, is a trebouxiophyte closely related to Chlorella-like unicellular coccoids, Stichococcus bacillaris and Prasiola species. This is the first robustly supported molecular phylogenetic analysis that places Prasiola in the Trebouxiophyceae. As shown previously, P. terrestris Groover & Hofstetter belongs to the Chaetopeltidales, Chlorophyceae. Dangemannia gen. nov. (type species: D. microcystis (Dangeard) comb. nov.), Floydiella gen. nov. (type species: F. terrestris (Groover & Hofstetter) comb. nov.) and Pabia gen. nov. (type: P. signiensis sp. nov.) are proposed.

Lagynion delicatulum Skuja is a first record for New Zealand freshwaters. Individual vegetative cells in nature and culture were sessile, aflagellate, and surrounded by a hyaline lorica lacking mineral deposits. Cells were uninucleate, had one or two chloroplasts with girdle lamellae and ring nucleoids, several mitochondria, and two to four basal-body-like centrioles. Cell division was followed by the release of one or both progeny from the parent lorica as biflagellate zoospores without eyespots. The anterior flagellum bore a tomentum of fine fibrils and two balanced rows of tripartite tubular hairs. The posterior flagellum was short, scarcely visible with light microscopy. A paraflagellar rod and paraflagellar vanes were associated with its axoneme. The flagellar apparatus consisted of two basal bodies and three microtubular roots. The coplanar basal bodies diverged from each other at an angle of approximately 130°. Simple transitional helices were present. No root that could be identified with the R3 root of other stramenopiles was present. Settling zoospores produced a few long pseudopods, and lost flagella by abscission. Cells forming loricas had a circumferential array of numerous short pseudopodia. Similarities in morphology and reproduction suggest that at least those Stylococcaceae with apparently uniflagellate swarmers form a monophyletic group. Flagellar apparatus similarities between Lagynion and Hibberdia suggest a relationship, but this is not supported by previously-published phylogenies reconstructed from molecular sequences. Convergent evolution of flagellar apparatus architecture is a possibility.

A novel member of the Calyptrosphaeraceae surrounded by a hyaline sheath, with only one chloroplast and without an emergent haptonema, is tentatively described as a species of Calyptrosphaera Lohmann. It has an interrupted body to its single pyrenoid and a unique microtubular root complement with only one crystalline root (CR) nucleating on root 2 (R2). At preprophase it produces a CR1, lending support to the idea that these crystalline roots contribute to the mitotic spindle. It shares numerous ultrastructural traits with the heterococcolithophorid Cruciplacolithus neohelis but, although it is tempting to consider it a haploid phase of this organism, is distinct from it.

The ultrastructure of Peridinium cinctum, was examined by serial sectioning with particular emphasis on the detailed construction of the flagellar apparatus. The pusular system of P. cinctum included two sac pusules in open connection with the flagellar canals; disorganized material was found inside the pusules and near the flagellar pores, indicating excretory activity of the pusules. Several cells had replicated basal bodies, which were oriented toward the cell apex. The functional basal bodies formed an angle of about 65° and were linked by a layered connective, a structure so far seen only in peridinioids. A transverse microtubular root looped around the transverse flagellar canal and nucleated several rows of microtubular extensions that lined most of the transverse sac pusule. A single-stranded root was associated with the surface of the longitudinal basal body almost at a right angle to the basal body triplets. A fibrous connective between the transverse striated root and the longitudinal microtubular root was absent. The striated collars encircling the flagellar pores had a complex structure and were linked by a large connective; a smaller fibrous connective was also found in one cell. An extension of the longitudinal striated collar lined part of the longitudinal sac pusule; it showed a tubular substructure and was perhaps contractile. Bacteria were present in the peripheral cytoplasm of the cell, enveloped by several unit membranes and surrounded by vacuoles; near the sac pusules they appeared disorganized with aggregated ribosomes, possibly the result of digestion.

The coldwater dinoflagellate Peridiniella catenata has been examined by light and electron microscopy. The fine-structure resembles that of other dinoflagellates with regard to the dinokaryon, the chloroplast enveloped by three membranes, and the pusule. The flagellar apparatus also resembles that of most other dinoflagellates. The main difference is a missing or reduced striated root connective between the longitudinal microtubular flagellar root and the transverse striated flagellar root. The amphiesma includes a scale-like layer on the outside of the plasmalemma. Another unusual feature is the presence of two distinct size classes of trichocysts, measuring c. 0.2×1 μm and c. 0.7×4 μm, respectively. In their detailed construction they resemble those of other dinoflagellate trichocysts. Peridiniella catenata differs from other gonyaulacoid dinoflagellates in the presence of chloroplasts with single-stalked pyrenoids and in details of the pusular complex. The presence of two size categories of trichocysts and the outer scale-like layer have not been observed in other gonyaulacoid dinoflagellates, indicating that P. catenata is not closely related to these dinoflagellates. However, the presence of two striated collar connectives in P. catenata, a feature hitherto observed only in gonyaulacoids, implies affinity to this group.

Cells of the potentially toxic dinoflagellate Alexandrium catenella have a complement of features typical of dinoflagellates, including dinokaryon, pusule and amphiesma. No endosymbiotic bacteria were found in the Californian strain examined, which is weakly toxic. The chloroplast consists of a central pyrenoid complex with radiating chloroplast lobes, an arrangement found also in certain other gonyaulacoid dinoflagellates. Cells are often arranged in few-celled chains and a cytoplasmic connection interconnects adjoining cells. Striated fibres line the attachment canal and also subtend the apical pore, making up an ‘apical fibrous complex’. The flagellar apparatus basically resembles that of other gonyaulacoids. However, Alexandrium catenella, Gonyaulax spinifera and Protoceratium reticulatum share the presence of two striated collar connectives and a single-stranded microtubular root associated with the longitudinal basal body, in addition to the multi-stranded root characteristic of dinoflagellates in general. Ultrastructural features indicate that these three species are closely related while Ceratium furcoides, another gonyaulacoid dinoflagellate, apparently lacks these features.

The fine structure of the flagellar apparatus of male gametes of Ectocarpus siliculosus has been studied in negatively stained whole-mount preparations of isolated flagellar apparatuses and by transmission electron microscopy of embedded whole cells and flagellar apparatuses. Reconstructions from serial sections revealed a single absolute configuration and new structural details of the flagellar apparatus. A set of 5 microtubular roots is associated with the 2 flagellar basal bodies: the major anterior root consisting of 9 microtubules originates at the anterior basal body and loops through the anterior part of the cell. Cytoplasmic microtubules originate from this root at the apex of the cell and splay out in a posterior direction through the cell, thus determining cell shape. A broad microtubular band composed of a 9-membered bypassing root and a 3-membered major posterior root runs across the basal bodies. Two additional flagellar roots, the minor anterior and minor posterior rootlets, consist of a single microtubule each. The proximal end of the posterior basal body is laterally connected to the anterior basal body by a cross-striated connective (deltoid band). The basal bodies are connected to the nucleus by a small rhizoplast, and several other fibrous structures are associated with the basal bodies. The results are discussed in relation to earlier observations on flagellar apparatus organization in brown algae.