Summary:
Features include 1) resupinate growth on wet wood, typically partly submerged, along shores of lakes and streams, 2) whitish color, the surface flocculose-porulose, then more continuous, the consistency soft, 3) spores that are long, narrowly fusiform, and smooth, at first thin-walled but after discharge a thick inner cyanophilic wall contracts from each end of the spore leaving the ends empty, 4) cystidia that are long, tubular, and protruding, and 5) a monomitic hyphal system, the hyphae with clamp connections.

Microscopic:
SPORES 16-20(25) x 5-7 microns, narrowly fusiform, smooth, at first thin-walled but after discharge the protoplasm contracts from the ends of the spore and surrounds itself with a thick, strongly cyanophilic secondary wall, "leaving the spore ends empty and eventually they shrivel" (if the contraction occurs stepwise, extra septa may occur in the empty spore end); BASIDIA 4-spored, 30-50(60) x 6-9 microns, "clavate, more or less sinuous", several oil droplets present at least when fresh, with basal clamp connection, old basidia often with one or several septa; CYSTIDIA numerous, (60)100-150(200) x 5-8 microns, tubular, tapering to obtuse apex, smooth, at first thin-walled, "then with more or less thickened walls"; HYPHAE monomitic, thin-walled, mostly 3-4 microns wide, distinct, with clamp connections, richly branched, branching preferably from the clamp connections, (Eriksson)

Notes:
Jaapia argillacea has been found in BC, Denmark, Norway, and Sweden, (Eriksson). Its distribution includes BC and ID, (Ginns).

Synonyms and Alternate Names:
Geoglossum proximum S. Imai & Minikata
Geoglossum subpumilum Imai