Penetration Phenomena and Facultative Parasitism in Alternaria, Diplodia, and Other Fungi

Abstract

1. Mechanical injury alone caused cells of wheat, sorghum, and broom corn to become markedly discolored near the points of injury; such discolored regions lacked callosities, auto-stained disks, red rings, and other infection phenomena. 2. The two hundred new diseases which resulted from the cross inoculations occurred under conditions very unlike field conditions. 3. All species of Alternaria placed on wheat coleoptiles induced the formation of callosities; all except three produced internal hyphae. 4. Alternaria infection of wheat coleoptiles is characterized by the formation of callosities by the host, and by the appearance of stained rings or disks around points of incipient infection. 5. Alternaria caused callosities to appear in seedling stems of wheat, oats, rye, barley, pop corn, sorghum, broom corn, cabbage, radish, turnip, tomato, Abutilon, soy bean, wax bean, watermelon, pumpkin, and muskmelon; Helminthosporium gramineum and Cephalosporium acremonium caused them to appear in field corn. 6. Dipl...