|Exserohilum species are common, and are most closely related to Drechslera and Bipolaris. Our laboratory does not separate Bipolaris, Drechslera, and Exserohilum species. The only morphological difference between Bipolaris and Drechslera is that Drechslera spores germinate from all cells (of the spore) and Bipolaris germinates only from polar cells. Exserohilum spores have an inner cup-like structure which is visible in the basal cell. Please see the page devoted to "Drechslera, Bipolaris, and Exserohilum" in the primary spore list: "Characteristics of Some Commonly Encountered Fungal Genera."