John Ralfs

Closterium is a genus of desmid, a group of charophyte green algae. It is placed in the family Closteriaceae. Species of Closterium are a common component of freshwater microalgae flora worldwide.

The Desmidiaceae are one of four families of charophyte green algae in the order Desmidiales (desmids). Desmids in the family Desmidiaceae consist of single-celled (sometimes filamentous or colonial), microscopic green algae. Because they are highly symmetrical, attractive, and come in a diversity of forms, they are popular subjects for microscopists, both amateur and professional. Within the desmids (Desmidiales), Desmidiaceae contains tens of genera and thousands of species, making it by far the largest family. Desmidiaceae includes some of the largest and most complex desmid genera, such

Micrasterias is a unicellular green alga of the order Desmidiales. Its species vary in size reaching up to hundreds of microns. Micrasterias displays a bilateral symmetry, with two mirror image semi-cells joined by a narrow isthmus containing the nucleus of the organism. This dual semi-cell structure is unique to the group of green algae to which Micrasterias belongs. Each semi-cell contains a single large chloroplast, the site of photosynthesis for Micrasterias. Chloroplasts within Micrasterias contain chlorophyll a and chlorophyll b and the enzymes required for photosynthesis. The sugar

Staurastrum is a large genus of desmids (Desmidiaceae), a group of green algae closely related to the land plants (Embryophyta). Members of this genus are microscopic and found in freshwater habitats around the world. The name Staurastrum comes from the Greek roots stauron, meaning "cross", and astron, meaning "star".

Euastrum is a genus of green algae of the Desmidiaceae family. It lives in acidic waters.

Desmidium is a genus of green algae, the type genus of the family Desmidiaceae. It has a cosmopolitan distribution in acidic, oligotrophic freshwater lakes and bogs. The genus name of Desmidium is derived from the Greek word 'desmos' (= ribbon, chain or bond). Desmidium consists of cells with two halves, called semicells; the cells are attached to each other at their ends, forming filaments. The cells can be longer or shorter than wide, with a median constriction (called an isthmus) where the two semicells join; the isthmus distinct or indistinct. Cells are oval or three- to five-angled in

Penium is a genus of green algae, and the sole member of the family Peniaceae. The genus contains about 39 species.

Hyalotheca is a genus of green algae, specifically of the Desmidiaceae. It has a cosmopolitan distribution and is found in acidic, oligotrophic freshwater habitats. Hyalotheca consists of chains of cells joined end-to-end to form filaments, which are surrounded in a thin or thick layer of mucilage. Cells are cylindrical with two identical halves called semicells; the isthmus (where the two semicells join) may be slightly constricted. Some species may have small protuberances near the cell median, making the cells appear somewhat lemon-shaped or triangular in apical view. The cell wall is

Docidium is a genus of algae belonging to the family Desmidiaceae. The species of this genus have a cosmopolitan distribution but are rare; they typically occur in acidic, oligotrophic waters. The name Docidium comes from the Greek term δοκίδιον (dokídion, 'small beam'), referring to its shape.

Tetmemorus is a genus of green algae, specifically of the Desmidiaceae.

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