A DISEASE OF THE BLACK LOCUST. 29 
leave the pores, but become imprisoned in the latter, by 
the ingrowing hyphae. The sporophores were found only 
on living trees. Their number varied considerably, from 
single large individuals on younger trees to thirty and forty 
on older trees, where they grow out on the smaller branches, 
in the extreme tree-tops. 
The characters above given agree well with the descrip- 
tion given for Polyporus (Fomes) rimosus, Berk. This 
fungus was described by Berkeley as growing on logs in 
Demarara, British Guiana. It is evidently closely related 
to Polyporus igniarius (L.) Fr., on the one hand, and 
Polyporus fulvus, Fr. on the other, differing from both in 
the extremely hard cracked upper surface, from which it 
derives its name; from the former, also, in the texture and 
structure of the internal parts and in its form, which so 
far as seen never approaches the globose, hoof form. Its 
color readily distinguishes it from Polyporus fulvus, Fr. 
As this fungus is essentially a wound parasite, preventive 
measures can be adopted by caring for the broken branches 
and other wounds. When but one tree of a group is in- 
fected, that tree ought to be cut down and burned so as to 
prevent infection of the other trees. Where possible the 
sporophores should be destroyed. 
The mycelium of Polyporus rimosus does not grow in 
the wood of the locust after it is cut from the living tree. 
Diseased locust wood when used for posts does not con- 
tinue to rot after it is placed in the ground. The fact that 
the mycelium ceases to grow in the wood after it is cut 
from the tree, or even after the death of the tree, suggests 
that the conditions which exist within the trunk of a live 
tree must be essentially different from those present after 
death. 
There must be some factors which favor the growth of 
the mycelium while in the wood of the standing tree which 
are changed or entirely inoperative after the tree is cut 
down. It is well known that many kinds of wood are 
