Daniel E. Wujek

THE SYSTEMATIC SIGNIFICANCE OF ACHENE MICROMORPHOLOGY IN CAREX RETRORSA (CYPERACEAE)

Scanning electron microscopy (SEM) was used to examine achene epidermal features of nine Carex species within sections Vesicariae and Lupulinae. Two major epidermal features are recognized in this study: the epidermal layers with one or two primary silicon bodies in each cell and the absence of any primary silicon body. Comparative data of achene morphology using SEM, and evidence compiled from previous investigations, support the placement of Carex retrorsa within section Vesicariae.

ULTRASTRUCTURE OF CHRYSODIDYMUS SYNUROIDEUS (SYNUROPHYCEAE)1

A clonal isolate of Chrysodidymus synuroideus Prowse was derived form a Sphagnum bog in northern Wisconsin and maintained in culture for over 3 years. Cultured colonies consisted almost exclusively of two cells attached at the posterior, each cell bearing two unequal flagella. Correlative light and electron microscopic observations revealed that colonies composed of smaller, ovate cells represented more recent products of cell division, while colonies of elongate cells were more mature. These results support previous taxonomic conclusions, based on light microscopic observations, of field‐collected specimens and body scale ultrastructure, that Chrysodidymus is a valid genus, and that two species described by Prowse on the basis of cell size differences, should be merged. In addition, ultrastructural studies of cultured Chrysodidymus demonstrated that this genus is a member of the Synurophyceae on the basis of characters related to flagellar morphology, basal body arrangement, and cytoskeletal ultrastructure. Chrysodidymus synuroideus resembles Synura sphagnicola in body scale structure, the presence of distinctive linear or clavate scales on both flagella, a relatively loose scale case, and acidophilic habital, Unlike S. sphagnicola, Chrysodidymus has no Pyrennoids, Peripheral (rather than axial) plastids, and a single posterior storage vesicle (rather than two peripheral storage vesicles).

The taxonomic position of Chaetopeltis

The flagella-like but immobile pseudocilia of the green alga Chaetopeltis are described. Examination of the pseudocilia reveals a similarity to those previously described for other members of the Tetrasporales. The taxonomic position of Chaetopeltis, in relation to other members of the Tetrasporales, is shown to be in the family Chaetopeltidaceae.

The Occurrence of Two Centric Diatoms New to the Great Lakes

New Great Lakes occurrence records of two diatom taxa, Terpsinoe musica and Biddulphia laevis, are presented for the southern basin of Lake Michigan.

A New Freshwater Species of Chaetoceros from the Great Lakes Region

Abstract A new taxon of diatom, Chaetoceros hohnii , known to occur in the Tittabawassee and Saginaw Rivers and Saginaw Bay, is described and illustrated. Its distribution and environmental parameters are presented.

Silica-scaled Chrysophyceae (Mallomonadaceae and Paraphysomonadaceae) from New Zealand freshwaters

Abstract Twenty-three species of silica-scaled Chrysophyceae were collected during late spring and summer from freshwater habitats in New Zealand and identified by examination of their scales with the transmission electron microscope. Four genera, Mallomonas and Synura (Mallomonadaceae), and Paraphysomonas and Spiniferomonas (Paraphysomonadaceae), were represented. The four species of Spiniferomonas, along with 11 species and one form in the other three genera, are reported for the first time. All the species found have distributions that are cosmopolitan or nearly so. A total of 42 species in three genera of Mallomonadaceae and two genera of Paraphysomonadaceae are now known in New Zealand. The flora consists both of cosmopolitan species and those so far known only from New Zealand, and probably is still significantly under-represented. Detailed knowledge of the New Zealand flora is necessary if silica-scaled chrysophytes are to be used in palaeoecological studies, or as an aid to water quality assessments.

Mallomonadaceae From Kansas

An examination by means of electron microscopy of phytoplankton samples from eastern Kansas revealed nine taxa of Mallomonadaceae. Five have not been previously recorded from Kansas. In addition, one is newly reported for North America.

Preservation of protists within decaying plants from geothermally influenced wetlands of Yellowstone National Park, Wyoming, United States

Abstract Decaying and partially silica-permineralized subfossil plant stems collected from geothermally influenced wetlands of Yellowstone National Park contain evidence of colonization by protists, including heliozoa and chrysophytes. Wetland pools in which the plants and heliozoans occur represent an extreme environment characterized by steady influxes of hot-spring water. Recorded physicochemical conditions in wetland pools reveal relatively high temperatures (often >35 °C), high pH (≤9.1), high conductivity (>3000 µS/cm−1), brackish salinity and elevated concentrations of toxic elements including antimony (Sb), thallium (Tl), mercury (Hg), and arsenic (As). This report contains the first observations of heliozoans and chrysophytes from intercellular sites within decaying plants and adds a previously unreported and extreme environment to their known habitats. Such settings are potential taphonomic windows for preservation of fossil protists.

SILICA-SCALED CHRYSOPHYTES FROM ECUADOR

Treinta crisofitas escamosas, obtenidos de 60 cuerpos de agua en Ecuador, fueron observados mediante microscopia electronica. Los taxones comprenden 27 Synuraceae (19 Mallomonas spp., siete Synura spp., y una especie de Chrysodidymus) y tres Chrysophyceae (dos Paraphysomonas spp. y una especie de Spiniferomonas). Todas son nuevos informes para Ecuador y un taxon (Mallomonas lychenensis f. ecuadorensis) se describe como nuevo. El numero de taxones por muestra vario de ninguno a diez

Microstructure of Pseudocilia of Tetraspora gelatinosa (Vauch) Desv.

Tetrvxporv gelatinosa (Vauch) Desv., which belong to Tetrasporaceae (Tetrasporales of the Chlorophyceae) is almost cosmopolitan in distribution. The moropholgy and reproduction have been studied by Smith (1950). This family differs from others of the order by the presence of two or more rigid processes, pseudocilia, at the anterior end of the cell. The pseudocilia often project beyond the colonial envelope (Geitler, 1931) and are visible only after staining. The term pseudocilia is unfortunate as these structures are not functional as cilia or flagella; they are motionless and when swarmers (zoospores) are produced, the pseudocilia are sloughed off (Fritsch, 1935).