During a twoyear period, beginning in the summer of 1973 and ending in the summer of 1975, a study was conducted on myxomycete bionta from bark of living trees growing in five widely separated localities within the Atlanta city limits. The objectives of the study were to determine (1) whether bark of living trees is a natural substratum for certain kinds of myxomycetes; (2) whether certain myxomycetes manifest affinities for certain species of trees; (3) whether seasonal variations exist in corticolous myxomycete occurrence; and (4) whether any correlation exists between the distribution of corticolous myxomycetes and tree habitats. Since two earlier studies of limited scope represent the only reports of systematic studies on corticolous myxomycetes of Georgia, a need has existed for more extensive information on this myxomycete bionta of the state. This study was undertaken in order to fulfill that need. To accomplish the objectives a total of 171 trees, representing 12 genera and 21 species, growing in five selected areas within the city limits of Atlanta, were chosen for the study. The genus and species of the trees used were Acer and A. saccharinum, Carya illinoensis and C. ovata, Cedrus deodara, Cornus florida, Diospyros virginiana, Liquidambar styraciflua, Liriodendron tulipifera, Ostrya virginiana, Pinus echinata and P. taeda, Prunus serotina, Quercus alba, Q. falcata, Q. nigra, Q. phellos, Q. stellata, and Q. velutina, Ulmus alata and U. americana. The five different localities used in this study included three relatively undisturbed wooded areas and two open park areas. The localities were (1) a wooded area in the Highpoint section; (2) a wooded hillside in the Collier Heights section; in the Beecher Circle section; and (4) two city parks, namely, Washington and Piedmont Parks. Specific plots were selected within each locality for sampling. Each plot was approximately 15 meters square and contained at least one tree of each species that was to be studied. In two of the localities, viz., Collier Heights and Beecher Circle, fallen debris on the forest floor was periodically examined in the field. Five different techniques were used to create conditions favor able for myxomycete development. These techniques were as follows: (1) a modification of the moist chamber technique originally used by Gilbert and Martin; (This modification involved the gradual soaking of bark pieces in sterile petri dishes by adding small volumes of sterile water intermittently as was absorbed by the bark, This practice reduced the possibility of spores being discarded, as may happen when the method of Gilbert and Martin is used.) (2) the placing of bark samples in polyethylene bags and attaching these bags to the sides of the trees from which they were collected; (Sterile distilled water was added to the bags in order to first saturate the bark pieces and subsequently maintain a high humidity.) (3) the removal of bark samples from trees and the incubation of these samples in petri dish moist chambers that were left in the field at the base of the tree from which the samples were removed; (4) the attaching of large waterfilled polyethylene bags to trees at about breast height; (The bags were perforated at the bottom by puncturing the corners and the middle with a few pin holes. This enabled water to slowly drip onto the bark below the bag and consequently keep the trunk in that region continuously moist.) and (5) the periodic examination of undisturbed bark of standing trees with a 1OX hand lens in a search for naturally developing slime molds. Field examinations of leaf litter were also made in order to determine whether myxomycetes that developed in moist chamber on bark samples also developed naturally on plant debris on the forest floor. A total of 46 species of myxomycetes was found during the two years of the study. Forty species of myxomycetes, representing 16 genera, appeared on collected bark samples during the course of the study, and six other species representing six genera were found on field observed leaf litter. The following species of myxomycetes were found: Arcyria carnea, A. cinerea and A. nutans, Badhamia nitens and B. obovata, Calomyxa metallica, Ceratiomyxa fruitculosa, Clastoderma debaryanum, Comatricha elegans, C. fimbriata, C. lurida, C. nigra and C. pulchella, Cribraria minutissima and C. violacea, Dictydium cancellatum, Diderma hemispaericum, Didymium difforme, D. iridis and D. squamulosum, Echinostelium minutum, Enerthenema papillatum, Fuligo septica, Hemitrichia stipitata, Lamproderma scintillans, Licea erecta, L. kleistobolus and L. operculata, Lycogala epidendrum, Macbrideola cornea, M. decapillata, M. martini, M. scintillans and M. synsporos, Metatrichia vesparium, Perichaena chrysosperma and P. minor, Physarum cinereum, P. crateriforme, P. decipiens, P. leucophaeum, P. nutans and P. viride, Stemonitis axifera, S. flavogenita, S. fusca and S. virginiensis The data from this study shows that some myxomycete species will develop only on bark from living trees, some species develop only on forest floor debris, and some species will develop on bark of living trees as well as on fallen debris. The species that appeared on fallen debris as well as on tree bark were Arcyria carnea and A. nutans, Physarum cinereum, P. nutans and P. viride, Stemonitis axifera and S. fusca. The species that were found on bark from living trees but were not found on fallen debris were Badhamia obvata, Clastoderma debaryanum, Comatricha fimbriata, C. elegans, and C. nigra, Cribraria minutissima, C. violacea, Didymium squamulosum, Licea erecta, L. kleistobolus and L. operculata, Macbrideola synsporos, Perichaena chrysosperma and P. minor, Physarum crateriforme, P. decipiens, and P. leucophaeum. The species of slime molds that were found on forest floor litter but were not found on bark of living trees were Ceratiomyxa fruitculosa, Dictydium cancellatum, Fuligo septica, Hemitrichia stipitata, Lycogala epidendrum, and Metatrichia vesparium. Echinostelium minutum is a ubiquitous species for it was common on bark from living trees as well as on fallen plant debris. Throughout this study variations were noted in the number of species of slime molds appearing on incubated bark samples during different seasons of the year. Echinostelium minutum appeared throughout the year on bark of all trees sampled except Acer negundo, A. saccharinum, Cedrus deodara, and Quercus phellos. Didymium squamulosum was found throughout the entire collecting period, except for the spring of 1974. Except for the summer of 1973, Comatricha fimbriata appeared on bark samples collected each season over the twoyear period of study. In some instances a slime mold may have appeared during a particular season in one year and may not have been found the following year during the same season. For example, Arcyria nutans was found during the winter of 1974, but was not found during the winter of 1973. Comatricha lurida appeared during the spring of 1974. Comatricha pulchella appeared only during the winter of 1974 as did Didymium difforme. Some slime mold species appeared only once during the course of the study. Macbrideola cornea and M. decapillata, Physarum cinereum, and Stemonitis axifera, are examples of species that were found once. Based on the data from this study, bark of living trees appear to represent a natural substratum for some species of myxomycetes. Some general affinity is apparent between some species of trees and some species of myxomycetes, depending upon the locality. Also, the appearance of some species of corticolous myxomycetes may vary with the season of the year, and some correlation appears to exist between the distribution of some myxomycete species and tree habitat. Some of the myxomycetes found in this study represent species previously unreported from the state. Those species are Calomyxa metallica, Clastoderma debaryanum, Badhamia nitens, B. obovata, Licea erecta, Macbrideola cornea, M. decapillata, M. martinii and M. synsporos, Perichaena minor, Physarum crateriforme, P decipiens and P. leucophaeum.
