Seven species of Alternaria, 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. oleracea Milbr., and A. Raphani n. sp. The latter has been isolated only from radish seeds. Two species occur on carrots, A. Dauci (Kühn) n. comb., and A. radicina Meier, Drechsler, and Eddy. A species close to A. Dauci has been isolated from flax and is described as A. linicola n. sp. The name A. tenuis auct. 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.