Stages of Development in Rhizomorphic Thalli of Armillaria mellea

SUMMARYThe rhizomorphs of Armillaria mellea are grown easily in pure culture and lend themselves readily to precise experimentation as well as to classroom use. This paper contains a description of the general aspects of development in a rhizomorphic thallus and is based upon the study of many monosporous isolates from several sources. Thallus development has been divided into 5 stages (summarized in Fig. 5): pre-emergence of rhizomorphs, emergence, lag phase of rhizomorph growth, linear phase, and terminal phase. Some details of growth and anatomy are also described and illustrated. The paper is intended primarily as the foundation for several future experimental papers about specific aspects of rhizomorph development, but it will also be useful to anyone desiring to grow rhizomorphs of A. mellea in pure culture. This species is particularly suitable for laboratory demonstrations of growing rhizomorphs and of fungal bioluminescence, and the methods described here for isolating and culturing the fungus may be considerably simplified for such purposes.