426 Journal of Agricultural Research 



Vol. V, No. lo 



SPOROPHORE OF STEREUM vSUBPILEATUM 



The sporophores of 5. suhpileatum 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. 5. 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. XI^I, 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. Xlyl, 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 XLI, fig. lo), 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. 



Living 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 THJE 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., i 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 ^ 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/x; cystidiB 

 incrusted, colorless, becoming brownish where buried in older layers of 

 the hymenium, cylindrical, 25 to 40 by 6 to S^t, not present in the inter- 

 mediate or tramal layer. 



' Ridgway, Robert. Color Standards and Color Nomenclature. 43 p., 53 col. pi. Washington, D. C. 

 1912. 



