Corticolous Myxomycetes V: Observations on the Genus Echinostelium

Abstract

SUMMARYSystematic screening of bark samples from living trees and vines placed in moist chambers has resulted in the discovery of two new species of corticolous Myxomycetes, Echinostelium arboreum and E. coelo-cephalum, and collections of E. fragile, the latter previously known from only a few localities. Echinostelium arboreum is characterized by its yellowish color, persistent peridium, prominent columella extending to the center of the sporangium, and a rather stout system of dichotomously branching, nonanastomosing capillitial threads firmly attached to the peridium. Echinostelium coelocephalum is characterized by its globose, sporelike columella, the absence of a capillitium, and the adherence of its spores by disjunctor pads into a layer forming a hollow sphere. A detailed description and the first photomicrographs are provided for E. fragile. A discussion of the use of bark cultures in obtaining and harvesting species of Echinostelia is included. Phylogenetic relationships in the Echinostelium—Clastoderma complex are discussed from the standpoint that E. arboreum is an evolutionary link leading to the higher Myxomycetes. A key is provided to the published species of Echinostelium.