426 
Journal of Agricultural Research 
Vol. V, No. 10 
SPOROPHORE OF STEREUM SUBPILEATUM 
The sporophores of 5 . subpileatum have been found by the writer 
only on dead trees or on dead areas on living trees. They usually occur 
on the fallen trees which had this rot while living. S. subpileatum 
apparently does not attack the. living sapwood and therefore has no 
chance to fruit unless the diseased heartwood is exposed by the death 
of the tree or by the breaking off of the trunk or of a branch. When an 
oak whose heartwood is attacked by this fungus is felled, the fungus 
continues to grow in the heartwood of the felled tree (PI. XU, fig. 8) 
and also grows outward into the sapwood. When the actively growing 
mycelium reaches the surface of the sapwood, the thin shelving sporo¬ 
phores (PI. XLI, fig. 9) are formed in the cracks between the bark, 
or if the bark has been burned off or has fallen off, large numbers of 
sporophores, often conchate in shape (PL XU, fig. 10), are formed 
over the entire surface of the fallen tree. These sporophores usually 
form in long, continuous parallel lines. The .individual sporophores 
range from 0.25 to 2 inches in width, depending on their age. 
Uving trees with this rot when felled usually lie for two or more 
years before any sporophores are formed. After sporophore formation 
once commences, the sporophores usually continue to grow for many 
years; therefore a tree or log culled for this rot in a lumbering operation, 
if not destroyed, will after one or two years be a menace for years to 
the future health of the forest. 
DESCRIPTION OF THE SPOROPHORE OF STEREUM SUBPILEATUM 
Pileus rather thick, medium-sized, coriaceous, firm, drying rigid and 
hard, sessile, dimidiate, conchate, subimbricate, often laterally connate, 
usually effuso-reflexed, decurrent onto the wood for 0.5 to 2 cm., 1 mm. 
thick by 0.5 to 6 cm. wide (measured from front to rear of sporophore) 
and 2 to 12 cm. or more broad, perennial, attached to substratum by a 
thin subiculum of densely woven Mars yellow 1 hyphae; surface finely 
tomentose at first, becoming glabrate with age, multizonate, older zones 
drab gray, finally becoming very indistinct and nearly glabrous, often 
radiately furrowed, marked with several concentric furrows of variable 
width and depth; margin thin, undulate, often incurved, strongly tomen¬ 
tose, tomentum from light buff to Mars yellow; hymenium inferior, 
sometimes stratose, changing color when injured and moistened, often 
concave, even, light buff; basidia simple with four sterigmata; spores 
colorless, even, broadly oval, flattened on one side, 4 to 5 by 3/4; cystidie 
incrusted, colorless, becoming brownish where buried in older layers of 
the hymenium, cylindrical, 25 to 40 by 6 to 8/z, not present in the inter¬ 
mediate or tramal layer. 
1 Ridgway, Robert. Color Standards and Color Nomenclature. 43 p. t 53 col. pi. Washington, D. C. t 
1912. 
