A Biometric study of the conidia of Macrosporium and Alternaria

Abstract

Alternaria and Macrosporium are closely allied genera of the Hyphomyctaceae, both being included in the section Dictyosporae of the Dematicae. They are differentiated by their methods of conidia-formation. In Macrosporium a conidiophore bears at its apex a single conidium, which attains its full size, matures, and finally becomes detached. In the case of Alternaria, the conidiophore produces at its apex a chain of conidia, each of which is morphologically identical with the single conidium of Macrosporiurn. This chain of conidia produced by Alternaria eventually becomes broken up into individuals which cannot be distinguished from a detached conidium of Macrosporimn. It is, therefore, only possible to refer a particular species to one or other of these two genera when the manner in which the conidia are produced has been determined. Consequently, many species have been incorrectly placed, owing to inaccurate observations on the conidia and method of conidia-formation. The abundance of species apparently placed indiscriminately in either genus and having synonyms in the complementary genus is evidence of the fact that these two genera are much confused. Thus Alternaria solani, Sorauer= Macrosporium solani, E. & M.