Attempts to inoculate Paspalum notatum and P. laeve with Myriogenospora atramentosa and Sporobolus poiretii with Balansia epichloë through inflorescences, seed, seedlings, leaf whorls, and cut stubble failed. Both fungi were culturable biotrophs on several warm-season perennial grass species. They overwintered in dormant buds and produced systemic infections of new shoots the next year. Mycelium of M. atramentosa lay on the surfaces of leaf primordia in buds and growing points of Eremochloa ophiuroides, P. laeve, and P. notatum. Near the tip on the upper surface of developing leaves it thickened into stromata in which sporocarps were produced after the leaf emerged from the sheath. The fungus did not penetrate the host, and no alterations in the host cuticle could be demonstrated with electron microscopy. Mycelium of B. epichloë was intercellular in buds, stems, and leaves of S. poiretii and Chasmanthium laxum. In localized areas on the upper leaf surface, hyphae emerged between epidermal cells or through stomates and formed a superficial fertile stroma. When hyphae grew laterally beneath the cuticle, electron-transparent pockets appeared in the overlying cuticle, and the cuticle disintegrated.