Studies of Cintractia axicola. I. Development of the sorus

Penetration of the host and development of the sorus of the smut Cintractia axicola on plants of Fimbristylis dichotoma and Cyperus rotundus was studied. Following germination of the teleutospores dikaryotic hyphae of promycelial origin penetrate the epidermis of the peduncle directly. From the point of penetration mycelium spreads mostly intracellularly through the tissues of the host. The cells of the epidermis become filled with monokaryotic mycelium which constitutes the fungal sheath. Internal to the epidermis, mycelium which is dikaryotic accumulates first in the subepidermal cells and then progressively occupies tissues of the peduncle. A stroma, pockets of sporogenous tissue, and a columella form. Nuclear fusion occurs in developing spores at the time they are differentiated from the parent hyphae. Sori may form in florets, groups of florets, or whole spikelets. The mode of differentiation of hyphae giving rise to sheath, stroma, spores, and columella is the same as described for sori which form at the bases of peduncles.