Biosystematics of the myxomyxcete Physarum melleum

Nineteen isolates of the myxomycete Physarum melleum derived from sporangia collected in the field or from moist chamber cultures were grown from spor e to spore on agar. Eighteen of the isolates were obtained from the island of Puerto Rico and one from Costa Rica. These isolates had bright yellow pl asmodia, grew well in culture and produced typical sporangia with the excep tion that peridial calcium carbonate deposits were sometimes scarce and whe n present often lacked the characteristic yellow to dull orange coloration usually reported for the species. All nineteen isolates were found to have a nonheterothallic reproductive system and the plasmodial fusion studies in dicated that most of these isolates were genetically distinct from one anot her.