Dictyostelium Aureo‐stipes and Dictyostelium Tenue: New Species of the Dictyosteliaceae

Three new cellular slime molds, Dictyostelium aureo‐stipes sp. n., D. aureo‐stipes var. helvetium var. n. and D. tenue sp. n., are described which possess characteristics heretofore unrecorded in the Dictyosteliaceae. The two species are unlike in dimensions and complexity of form, yet show a number of features in common, and may in fact be closely related. D. aureo‐stipes var. helvetium is relatively large and robust, forming multiple‐branched fruiting bodies without the regularity of form found in Polysphondylium, yet tending toward symmetry when well‐developed. The golden‐yellow stipe is a distinguishing feature of D. aureo‐stipes and is even more pronounced in var. helvetium. D. tenue is smaller and simpler in form. The degree of branching is much reduced, and oftentimes a solitary sorus terminates a delicate stipe composed of a single tier of cells. Both species are quite sensitive to environmental conditions, particularly temperature, for optimum development occurs within relatively narrow ranges.