|Helminthosporium spores superficially resemble Drechslera, Bipolaris, and Exserohilum spores but the mechanism of sporulation is quite different. The taxonomy of this entire group has been widely debated. Helminthosporium is rare, and has never been isolated by our laboratory. The culture examined by us as a study culture came from the southern U.S. from Dr. Luttrell, one of the key players in the taxonomic saga. The antigen labeled "Helminthosporium" in use by allergists for skin testing has been found to be either Drechslera, or Bipolaris. No cases of infection caused by a true Helminthosporium have been reported in humans or animals. No information is available regarding toxicity. Allergenicity has not been studied, although cross reactivity may exist between all the above mentioned genera. Natural habitat includes dead stems of herbaceous plants, and twigs and branches of many different kinds of trees. Helminthosporium solani is the cause of "silver scurf" disease in potatoes.