Euphorbia arceuthobioides flowering yellow

Flowering of Euphorbia arceuthobioides may occur in clusters such as here. The terete (cylindrical) upper stems fork once or twice to present small yellow cyathia (false flowers) on their short green stalks. The older stalks have developed a whitish covering.

There are short, green, leaf-like bracts not yet dropped off the bases of some of the cup-shaped involucres. The cyathium of this species is unisexual with five glands and five oblong, fringe-toothed lobes (JSTOR).