Florida Agricultural Experiment Station


 It was equally surprising to find that oak and occasionally
other hardwood roots extensively invaded by the mycelium of
the Clitocybe root rot fungus occurred under each of these citrus
trees and that some of these infected roots were in contact with
one or more roots of the citrus trees in apparently all cases.


Fig. 21.-Grapefruit trees attacked by Clitocybe mushroom root rot, show-
 ing bark lesion at base on left and a partially dried cluster of fruiting
 bodies developed at base on right.
The inference is that the oak and other hardwood roots which
were left in the land when it was cleared became infected by the
Clitocybe root rot fungus and that these roots served to transmit
the fungus to the roots of the citrus trees. It was also observed
in several instances that where an infected citrus root crossed
or otherwise came into contact with other citrus roots, the root
rot fungus was transmitted to these roots. The majority of the
attacked roots of the citrus trees, as well as the old oak roots,
exhibited an abundant development of the mycelium of this
root rot fungus except in those cases where they were fairly well
decayed or the mycelium had run its course.
 Unlike the development of Clitocybe root rot observed in most
other attacked trees, in citrus trees the mycelium rarely seems to
develop very far above the ground line. The mycelium, or vege-