Marasmius siccus is a tiny mushroom that grows in leaf litter. The caps were 1 cm or a little more, orange-brown, glabrous, slightly rough, pleated, convex to bell-shaped. The gills were quite distant and pale, sometimes splitting toward the margin. The stem was very thin (around 1 mm or less on some), pale toward the apex, then dark and shiny below. All the specimens I gathered were shorter than 6 cm.
A key feature to separate this from the closely related Marasmius pulcherripes is the spore size. These measure 22 μm. The spores of M. pulcherripes measure 11-15 μm, according to Mushrooms of the Midwest.