Annual report of the North Carolina Agricultural Experiment Station . he left-hand branch in Fig. 41, and somewhat enlargedin Fig. 42. 2. Mycelial ribbons, rhizomorphic structures extending lengthwise of thetwigs and petioles. (Fig. 43.) The sclerotia originate as white masses of interwoven mycelium, whichwhen mature become rich chestnut brown in color. They are formed ingreat abundance upon the twigs of the current year, especially upon thelower, shaded, damp side, but very sparingly or not at all upon the petioles 78 THIRTY-SECOND ANNUAL REPORT, 1909. or leaves. On two-year-old twigs the scl
Annual report of the North Carolina Agricultural Experiment Station . he left-hand branch in Fig. 41, and somewhat enlargedin Fig. 42. 2. Mycelial ribbons, rhizomorphic structures extending lengthwise of thetwigs and petioles. (Fig. 43.) The sclerotia originate as white masses of interwoven mycelium, whichwhen mature become rich chestnut brown in color. They are formed ingreat abundance upon the twigs of the current year, especially upon thelower, shaded, damp side, but very sparingly or not at all upon the petioles 78 THIRTY-SECOND ANNUAL REPORT, 1909. or leaves. On two-year-old twigs the sclerotia are darker in color, shriveledand sometimes cracked, and it is doubtful if they live longer than throughthe summer following their origin. Upon badly affected trees it is possibleto find sclerotia upon older twigs, two, three, four, or five years old, the sizeof the sclerotia being diminished by waste, shrinking, and weathering, withthe age of the wood upon which they rest. Sclerotia are sometimes foundupon fruit, though much less frequently than upon Fig. 43.—Rhizomorphic mycelium upon apple twigs and petioles; weftof floccose mycelium on inferior surface of leaf. The mycelial rhizomorphic structures when young are white, but as theyage they rapidly assume a characteristic glistening brown appearance. Theyextend in a general longitudinal direction, and usually remain unbranched be-tween the nodes, though they sometimes branch and anastomose, forminga small plexus. Occasionally branches diverge to courses leading around thetwig. At the base of each small twig the ribbon usually branches, a portionof it passing onto the smaller twig. Branches of these mycelial ribbons also follow up the petioles and themain veins of the leaves, eventually spreading out, separating into single HYPOCHNOSE OF POMACEOUS FRUITS. 79 mycelial threads and becoming lost to the naked eye. The mycelial ribbonson the older wood die and often weather away, though they adhere withconsiderable
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