Seven species ofAlternaria, of which six are definitely pathogenic, have been isolated from agricultural seeds. Cruciferous plants are attacked by three distinct species;A.Brassicae(Berk.) Sacc.,A.oleraceaMilbr., andA.Raphanin. sp. The latter has been isolated only from radish seeds. Two species occur on carrots,A.Dauci(Kühn) n. comb., andA.radicinaMeier, Drechsler, and Eddy. A species close toA.Daucihas been isolated from flax and is described asA.linicolan. sp. The nameA.tenuisauct. is used to include the generally saprophytic forms that have been isolated from seeds of a wide variety of plants. They exhibit many variations in cultural characters, spore markings, etc., but all have spores falling within the range 20–50 × 10–16 μ.