Rhizoctonia belongs to a group of fungi called the "Mycelia Sterilia." These fungi do not produce asexual spores, but grow by producing thin, vegetative strands called hyphae (Figure 20). In recent years, the sexual stages, or teleomorphs, of many Rhizoctonia species have been characterized and classified in the basidiomycete genera Thanatephorus, Waitea, and Ceratobasidium. However, these sexual stages are rarely seen in nature, so the classification in the Mycelia Sterilia has been maintained. Because Rhizoctonia species often do not produce spores, these fungi are identified by characteristics of their hyphae. Rhizoctonia hyphae produce branches at right and acute angles to the main hypha, the branch hypha is slightly constricted at the branch origin, and there is often a septum near the branch origin (Figure 20). Rhizoctonia species also produce specialized hyphae composed of compact cells called monilioid cells (Figure 21). The monilioid cells fuse together to produce hard structures called sclerotia (Figure 22), which are resistant to environmental extremes, allowing the fungus to survive adverse conditions.