. Bulletin. Natural history; Natural history. June 1941 CARTER: OAK DISEASES IN ILLINOIS 221 little branched, mm. in diameter, and they contain cream to white hyphal strands. The rhiznmorplis that develop in the cambial region of the roots and tree trunks are dark red to reddish brown, Hattened, much branched, mm. broad, and they contain cream to white hyphal strands. Sporophores of Arniillaria develop, usu- ally in October in Illinois, on the dead bark of the trunks and the roots of in- fected trees. Also they may be found on the ground at or near the base of the infected trees an
. Bulletin. Natural history; Natural history. June 1941 CARTER: OAK DISEASES IN ILLINOIS 221 little branched, mm. in diameter, and they contain cream to white hyphal strands. The rhiznmorplis that develop in the cambial region of the roots and tree trunks are dark red to reddish brown, Hattened, much branched, mm. broad, and they contain cream to white hyphal strands. Sporophores of Arniillaria develop, usu- ally in October in Illinois, on the dead bark of the trunks and the roots of in- fected trees. Also they may be found on the ground at or near the base of the infected trees and sometimes at distances of several feet from them. A group of immature sporophores taken from the root of an oak ma\' be seen in fig. 39. MISCELLANEOUS FUNGI CylindTOsporium Cylindrosporiuiii was found fruiting in the diseased tissue of one dieback specimen of shingle oak. The fungus was not grown in culture from this specimen nor from any other specimens of diseased oak. How- ever, Coryneuin was grown in culture from the diseased tissue of this specimen and was most likely the fungus responsible for the dieback. The Cylindrosporium evi- dently developed in the bark after the branch had become infected with Cory- neuin. The diseased bark of this shingle oak specimen is light to dark brown, slighth- shrunken and for the most part smooth ; however, where the numerous Cylindrn- sporiiint acervuli have been produced there. Fig. 40.—Accrvulus of Cyiindrosporitim on shingle oak. A vertical section of an acervulus whicli shows the position ot the acervulus in re- lation to the host tissues. X 75. are blisters. An acervulus is shown in ver- tical section in fig. 40. Acervuli are dark brown to black, pulvinate and immersed. Thev become erumpent at maturitv and are 530-1100 ^ in diameter and 130-400 /J, high. The acervuli arise fundamentally in the phellogen-phelloderm region of the bark and at first cause very little distor- tion and disintegration of the cortical cells. As they expa
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