An Ultrastructural Study of Spore Germination in the Myxomycete Arcyria Cinerea

SUMMARY

Mature spores of Arcyria cinerea are typically uninucleate and contain a complement of cellular constituents including ribosomes, mitochondria, endoplasmic reticulum, vacuoles, a polysaccharide storage material and numerous spherical bodies thought to be lipid in nature. The spore wall consists of a very thin, electron dense, outer component and a much thicker inner component which is virtually electron transparent. Once spores are placed in water the germination process is initiated. Two of the most significant events taking place during germination are the disappearance of the polysaccharide material and the numerous lipid bodies. By the time the protoplast is prepared to emerge from the spore case a pair of centrioles and a Golgi complex appear. Germination is accomplished by a breaking or splitting of the spore wall and the emergence of a myxamoeba or a flagellated swarm cell. Swarm cells are typically biflagellate with the flagella arising from the centrioles which function as basal bodies.