Development of the Helvellineae. I. Helvella elastica

Abstract

The mycelium of Helvella elastica is subterranean. Its cells are multinucleate. The fruiting body arises from clumps of thick short-celled filaments. This fruiting body is quite early surrounded by an envelope which is transitory and breaks up irregularly. Closely associated with the veil in early stages, but persisting throughout the life of the fruiting body, is an external layer of club-shaped palisade hyphae. Certain large irregular cells occurring in all parts of the fruiting body (except the stem) apparently have the function of storage organs. The "ascogenous hyphae" arise as a clearly differentiated subhymenial complex of filaments. From this layer grow out vertical branches whose end cells contain usually two nuclei. Hooks are formed by these end cells, while the proximal part of the branch degenerates. The process from the first-hook, without fusion of its two nuclei, may proceed to form a second and similar hook. From this second a third may arise, and so on, up to the number of at least six, the process from the last becoming the ascus after nuclear fusion. In any hook of such a series a "fusion" or "anastomosis" of the terminal and antepenultimate cells may take place, the nuclei of both passing into a process arising from the former. This process is equivalent to that springing from the penultimate cell, and conducts itself in the same way. The two nuclei which fuse to form the primary ascus nucleus are directly descended by conjugate division from the two which occupied the end cell of the young ascogenous hypha. No structure having the conventional form of an ascogonium was found.