AUTOBASIDIOMYCETES 475 



extend outward, perpendicular to this sheath. Within this zone 

 there is next found a dense, resistant layer of small-celled pseudo- 

 parenchymatous tissue, surrounding a medullary cylinder com- 

 posed of lighter, more delicate, conducting cells. At the base of 

 the tree the general mycelium produces a definite white rot. 



In this country sporophores are usually produced during favor- 

 able weather in September, October, and early November. They 

 may appear at the collar of the tree, or upon the roots, etc. More- 

 over, a year or two after forest land has been cleared for pasturage, 

 the sporophores may appear in enormous quantities on the slightly 

 sunken roots. These fruit bodies are usually produced in clusters. 



Fig. 236. Armillaria mellea on exposed Roots in a Meadow 



arising either directly from a felted mycelium or from rhizomor- 

 phal aggregations. The mature sporophore (Fig. 236) consists of 

 a fleshy cap, ordinarily 5-15 cm. broad, borne upon a central stalk 

 often 12-18 cm. long, with cartilaginous rind and spongy center. 

 The stem is yellowish in color above, but usually brown below, with 

 a more or less persistent annulus, or attached collar. The cap varies 

 from convex to slightly umbonate. It is yellow to orange-brown in 

 color, the center of the cap when younger being often covered with 

 papilliform, brown, or sooty scales. The lamellae are white or slightly 

 discolored, distinct one from another, and somewhat decurrent upon 

 the stem. In taste this plant is distinctly acrid, sometimes very 

 harsh. It is, however, considered to be edible by those who have 

 developed a taste for a variety of mushroom flavors. 



