Observations on chytridiaceous parasites of phanerogams

Summary

A study of the morphology and life cycle of two Physoderma taxa occurring on Eleocharis spp. in Michigan is presented in detail. Both fungi possess almost identical endobiotic and epibiotic stages. They differ significantly with respect to the ease of germination of the resting spores, those on E. compressa being difficult to germinate whereas those from Eleocharis sp. from the vicinity of Ann Arbor do so readily.

Resting spore stages of other collections, American, Polynesian and European, including the type of Physoderma heleocharidis (Fuckel) Schroeter, when compared, do not differ significantly from one another. P. schroeteri Krieger described from Scirpus is hardly distinguishable from P. heleocharidis on resting spore stage alone. Furthermore, we have successfully produced mature thalli and resting spores of the Physoderma on Eleocharis from Ann Arbor on Scirpus actus. Other such successful cross incculations will be needed before we will say with certainty P. schroeteri is not distinct from P. heleocharidis.

Enough similarity is to be found in all the fungi on Eleocharis to place them for now, at least, in a single taxon, Physoderma heleocharidis. Future work with living material will no doubt necessitate a different treatment. An expanded technical diagnosis of P. heleocharidis based on our studies is included.