Summary:
Features include tiny, nearly spherical fruitbodies that open to become urceolate, the exterior dark olivaceous brown to blackish and slightly striate, the spore-bearing area grayish, the margin fringed and sometimes paler than the exterior, the stem rudimentary, growth on Spiraea, and microscopic characters.

Microscopic:
spores 20-35(45) x 2.5-3.5(4.0) microns, "elongate-fusiform to subfiliform, occasionally slightly subclavate, straight or slightly curved", pointed at ends, colorless, 3-septate, more or less fasciculate in the ascus; ascus 8-spored, (75)90-110(125) x (5.0)7.0-9.0(10.0) microns, cylindric to cylindric-clavate, tapering in lower part to a slender stem, pore blue with iodine; paraphyses about 1.5-2.0 microns wide, filiform, colorless, septate, simple or branched, "the tips not or very slightly swollen, not forming an epithecium"; conidia 15-25 x 2.0-3.0(4.0) microns, "elongate-fusiform to subfiliform, straight or slightly curved, sometimes sigmoid, pointed at ends", colorless, 1-celled to 4-celled; conidiophores 10-25 x 1.5-2.0 microns, sometimes larger, cylindric-subulate, colorless, septate, branched, "bearing conidia at the tip"

Notes:
Collections were examined from BC, WA, ON, PQ, NH, NY, and PA, (Groves).

Synonyms and Alternate Names:
Rhizina inflata (Schaeff.) P. Karst.
Rhizina zonata Berk.