The Development of the Ascocarp of Leotia

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Abstract
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 separate two pairs of sisters. Either of these pairs may divide and give rise to the nuclei of another hook or fuse to form the nucleus of an ascus. Any of the methods described above by which the number of asci is increased may be repeated many times. The relationship of the nuclei which fuse in a plant like Leotia is probably of no significance, since they are all in the same plant and are probably derived from a single nucleus with the haploid number of chromosomes. The vegetative hyphae form large storage cells in the hymenium. The nuclei in these cells frequently fuse to form a single large nucleus. The development of the ascocarp indicates that all of its structures are homologous with those of the Pezizineae, and that Leotia is closely related to the Pezizineae.

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