Two new species of Nitella (Characeae, Charophyceae) from arid-zone claypan wetlands in Australia

Two new species of Nitella Ag. are described. The species are dioecious and grow in temporary arid-zone wetlands called 'claypans'. Both have somewhat inflated, bicelluate fertile dactyls and neither species has mucus associated with the reproductive whorls. Nitella parooensis M.T.Casanova & J.LPorter is characterised by its apparently pluricelluate sterile branchlets with acute, conical end cells, inflated bicellulate dactyls and uniquely twisted oogonia and oospores. Nitella micklei M.T.Casanova is characterised by a crisp, inflated appearance, large antheridia and distinctive oospores. The ornamentation on the oospores of both species is essentially reticulate, but for N. micklei there are 1 -2 thickwalled meshes across the fossa, and in mature oospores of N. parooensis the 3-4 meshes have scattered, acute papillae within them