The ascogenous hyphae of Leotia have their origin at the base of the ascocarp, probably from a one-celled ascogonium. The asci are formed at the tips of the ascogenous hyphae in several different ways. In some cases a hypha forms a typical hook, consisting of a binucleate penultimate and a uninucleate ultimate and antepenultimate cell. In this case the two nuclei of the penultimate cell may fuse to form the nucleus of an ascus, or they may divide and give rise to the four nuclei of another hook. The uninucleate ultimate cell usually grows down and fuses with the antepenultimate cell, after which the nuclei of the two cells may give rise to the nuclei of another hook, or they may fuse to form an ascus. The walls separating the nuclei may fail to be formed without affecting the fate of the nuclei. In this process there is a conjugate division comparable to that in the rusts. Frequently the ascogenous hyphae do not become markedly bent, and in this case, when the two nuclei in the tip divide, a wall may sepa...