. Bulletin. Natural history; Natural history. 220 ILLINOIS NATURAL HISTORY SURVEY BULLETIN Vol. 21, Art. 6. Fig. 38.—Young sporophores of Armillaria. They were found developing in tlie soil about 1 foot from the base ol a bur oak tree and above the infected root. The reddish-brown to black rhizomorphs are attached to the young sporophores. X 1. white, heart-rot wood as well as from rhizomorphs, Armillaria ?neUea (Vahl.) Quel, was isolated. A culture of A. mel- lea with rhizomorphs that permeate the potato dextrose agar is shown in fig. 37. In the roots of many of the diseased oaks, rhizomorphs
. Bulletin. Natural history; Natural history. 220 ILLINOIS NATURAL HISTORY SURVEY BULLETIN Vol. 21, Art. 6. Fig. 38.—Young sporophores of Armillaria. They were found developing in tlie soil about 1 foot from the base ol a bur oak tree and above the infected root. The reddish-brown to black rhizomorphs are attached to the young sporophores. X 1. white, heart-rot wood as well as from rhizomorphs, Armillaria ?neUea (Vahl.) Quel, was isolated. A culture of A. mel- lea with rhizomorphs that permeate the potato dextrose agar is shown in fig. 37. In the roots of many of the diseased oaks, rhizomorphs of Arinillaria, shown with attached sporophores in fig. 38, de- velop in the cambial region and in root cavities. In the late stage of staghead, the rhizomorphs are frequently found under the bark at the base of the large roots and in the root crotches. Rhizomorphs may enter through wounds in the root crotches at or below the surface of the soil. Thev are present in the duff at the base of seri- ously infected trees and frequently are found spreading through the soil for dis- tances of 25 feet or more. In the earlv stage of staghead, rhizomorphs are asso- ciated with the death and rotting of the very small feeding roots. Gradual de- struction of these roots reduces the feed- ing capacity of the root system and limits the amount of foliage that can be sup- plied with plant food and water. An in- adequate supply of plant food and water causes the gradual drying back and dying of the extremities of the branches, and in time the affected trees show staghead. Armillaria infection at the base of a large root quickly reduces the amount of food and water supplied by the root and causes dieback or death of the branches that are supported by the infected root. Infections of this type in several roots cause the rela- tively sudden death of the tree. In the soil, rhizomorphs are dark red- dish brown to black externally, Please note that these images are extracted from scanne
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