Summary:
Postia ptychogaster may be found in its non-sexual stage (with chlamydospores) which typically precedes formation of the tube layer and pore surface (with basidiospores). The non-sexual (imperfect) stage is a soft, cream-colored cushion covered with minute spines, and its core becomes powdery gray-brown. The sexual fruitbody, up to several centimeters in diameter, often develops on the underside of this cushion and can form a semicircular or spatula-shaped cap or a spread-out layer on the substrate. There is sometimes a lateral stem. The cap when present is white and downy, while the pore surface is pallid. The description is derived from Ginns(28).
Postia ptychogaster is known in western North America from BC, WA, OR, and CA.
Cap:
"effuse to pileate, annual, dimidiate, sessile, spathulate or laterally stipitate, only several centimetres in diameter, when dry fragile, frequently developing on the lower surface of the imperfect stage" which typically precedes the development of the tube layer; imperfect stage "sessile, cushion-shaped", up to 4cm x 5cm, "soft, cream, surface covered with minute spines", "core becoming powdery, grey brown"; cap surface "white, azonate, finely pubescent"
Flesh:
context duplex, about 1.4cm thick with a dense, waxy, 0.4cm thick mycelial layer adjacent to tube layer, "from this dense layer hyphal strands permeate (like veins or roots) a soft, cottony mycelial layer" 1.0cm thick
Pores:
2(3) per millimeter, angular, "edges thin, lacerate", pore surface pallid; tubes pallid, up to 0.3cm deep
Stem:
none or lateral
Microscopic:
basidiospores 3.8-4.4 x 2.4-2.8 microns, elliptic to nearly oblong, "some narrowed slightly over the apical one-third", smooth, inamyloid, colorless, walls about 0.3 microns thick, cyanophilic, apiculus minute; chlamydospores 5.6-8.0(10.0) x 3.5-6.0 microns, elliptic to nearly oblong, "some with ends truncated", smooth, dextrinoid, pale yellow brown, cyanophilic, walls about 0.4 microns thick; hyphae with clamp connections, walls colorless and thin, of two types: 1) "in the cottony context typically curved", 2-3 microns wide, with "prominent clamp connections", and 2) "in the dense context adjacent to the tubes and in the strands, essentially parallel, straight", (2.4)3.0-5.0(8.0) microns wide; tramal hyphae "straight, vertically woven", 3-4 microns wide, walls typically 0.5 microns thick, "en masse weakly to moderately intensely dextrinoid"
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