Abstract
A HCl-thionine staining technique was devised for the simulta-neous demonstration of in situ mitochondria and their nucleoid in the plasmo-dium of Physarum polycephalum, as well as for isolated mitochondria from microplasmodia of the same organism. Light microscopy of samples stained by the method revealed that most mitochondria contained a particle-or rod-shaped nucleoid but an appreciable number of isolated mitochondria contained V-shaped mitochondrial nucleoids. Since such mitochondria containing V-shaped nucleoid were larger in size, it appears that these mitochondria may be dividing mitochondria.
