Electronic Flora of South Australia Family Fact Sheet
Thallus macroscopic, from a few centimetres to a metre high, light to dark green with similar photosynthetic pigments to the Chlorophyta and starch as the storage product. Habit characteristically of axes, each developed from an apical cell, anchored by rhizoids in muddy substrate, and bearing whorls of laterals of limited growth at nodes separated by comparatively long internodal cells. Nodes of relatively small uninucleate cells with two central cells and a ring of peripheral cells from which the whorled laterals and appendages develop. Internodes of a single, large, multinucleate cell, corticated or not by filaments originating from nodal cells. Stipulodes (one celled processes) commonly produced from the peripheral nodal cells, and similar bract-cells arise from branchlet nodes. Nuclear division phragmoplastic, cell wall of cellulose microfibrils.
Reproduction: Reproduction oogamous with complex antheridia and oogonia borne laterally on the branchlets and usually subtended by bracts. Antheridia globular, becoming orange-red, consisting of a central stalk cell which bears 8 primary capitula cells with elongate manubrium cells connected to 8 (rarely 4) outer shield cells which are united to form a sphere. The primary capitula cut off near their bases small secondary capitula cells, each of which produces several long, many-celled antheridial filaments with each cell producing a single biflagellate sperm. Oogonia at first naked but becoming surrounded by 5 spiral corticating filaments, closely adjacent soon after fertilisation, and which form 5 (or subdivided to give 10) coronal cells at the apex of the oogonium. Zygote usually becoming black with a thickened, resistant wall, especially between the spiral corticating cells.
Life history haplontic with zygotic meiosis.
Taxonomic notes: The Charophyta are sometimes regarded as a class of the Chlorophyta, but are highly distinctive in thallus construction and in their reproductive organs.
It is generally accepted that the Charophyta contain only a single class, order and family.
Members of the Charophyta are common in freshwater to brackish ponds and lakes with a muddy or silty bottom, and frequently appear in winter pools which dry in summer when the resistant zygotes perpetuate the species. Charophyta in general do not occur in marine situations, but in several parts of southern Australia Lamprothamnium papulosum is found in brackish to saline, largely to partly enclosed lakes adjacent to the sea; in some of these areas the salinity at times may be above that of normal sea water, though the Lamprothamnium may grow best under slightly lower salinities.
References: The Marine Benthic Flora of Southern Australia Part I
Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
State Herbarium of South Australia