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

摘要: 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 MT Casanova & JL Porter is characterised by its apparently pluricelluate sterile branchlets with acute, conical end cells, inflated bicellulate dactyls and uniquely twisted oogonia and oospores. Nitella micklei MT 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.