Dec. io, 1913 
Polyporus Dryadeus 
243 
rays. The bordered pits in the vessels are usually reduced to long, 
elliptical openings running transversely across the walls, and the bor¬ 
dered pits of the tracheids become large, round holes, which often coa¬ 
lesce, thus splitting the tracheids longitudinally. The pits of both 
large and small medullary rays are somewhat enlarged, while their radial 
and tangential walls are perforated with holes. 
Even in the early stages of the rot, when the discolored spots are 
beginning to show in the sapwood of the roots, the vessels have color¬ 
less hyphae in them, while in the later stages many of the vessels become 
filled with a mass of colorless hyphae having filaments 4/i or less in diam¬ 
eter. The wood-parenchyma fibers show enlarged pits and perforated 
radial walls, and the pits in the wood fibers are also enlarged. The walls 
of the medullary rays are much corroded and often disappear entirely. 
Only very slight evidence of delignification is shown by the chloriodid 
of zinc test. After standing 24 hours in this reagent there is a slight 
cellulose reaction in the walls of the vessels, tracheids, and wood fibers 
but none in the medullary rays. In making free-hand sections of the 
diseased wood the medullary rays and vessels are easily ruptured, owing 
to the thinning and weakening of the walls by the solvent action of the 
fungus. 
The concentric splitting of the rotted wood usually occurs in the zone 
of the larger vessels, which are weakened by the corrosion of their bor¬ 
dered pits and walls. The longitudinal splitting is caused by the coa¬ 
lescence of the enlarged bordered pits of the tracheids and the thinned 
walls of the medullary rays. The discolored areas seen in the earlier 
stages of the rot are due to the presence in the cells of the medullary 
rays, wood parenchyma fibers, and sometimes in the lumen of the wood 
fibers of a brownish liquid, which disappears before the white stage of 
the rot is reached. In the final stage of the rot the wood is somewhat 
spongy in texture and when dry is easily crushed between the fingers. 
Old sporophores were often found at different places on the collar of 
the diseased tree, due probably to the gradual rotting of the roots upward 
toward the stool of the tree and the formation of sporophores whenever 
a rotted area reached the collar of the tree or the underside of a root 
whose upper surface was exposed to the air. The sporophores are 
usually attached to the trunk of the tree at the surface of the ground, 
but they were also found on the exposed roots or even in rare cases on 
the ground, having been produced from hyphae issuing through the soil 
from diseased roots lying a short distance below. Only one sporophore 
was found on the trunk at a distance above the collar of the tree, and in 
this case two trees had grown together at the butts for a distance of 
12 inches. The rot had extended from the diseased roots upward in the 
injured sapwood of the oak along the juncture of the two trunks, and a 
small sporophore had formed 10 inches from the ground. 
17072 13— 5 
