Abstract
Oospore characteristics are described for charophyte species in New Zealand and a simple key to species is presented, based on consistent oospore features. Oospore dimensions measured using a light microscope and an image analysis system showed that some taxa could be distinguished on size. The ornamentation on the outer wall of oospores was described from both light microscopy and scanning electron microscopy and was particularly useful for distinguishing Nitella species, while striae number and basal features were helpful in identifying the remaining genera. Species oospore ornamentation is compared with the findings of previous workers and the need for revision of some species in New Zealand is raised. Taxonomic uncertainties involve New Zealand records for Nitella cristata , whereas intraspecific variations in oospore ornamentation within N. hookeri and N. pseudoflabellata indicate that additional taxa should be recognised.