Disease of Rubber caused by Ustulina Zonata. 159 
described by Brooks and Sharpies (1). These conspicuous black 
zones are caused by the fungus forming a kind of sclerotic plate in 
the tissues, the difference between this aggregation and a typical 
sclerotium being that the latter does not include within it portions 
of the tissues of the host. These black zones differ from rhizo- 
morphic strands in the same respect. The fungus invades the tree 
either in the collar or in one of the roots from either of which it 
advances, spreading more rapidly in a longitudinal than in a lateral 
direction. In advanced stages of disease several of the laterals and 
the tap root may be dead and the fungus may have progressed two 
or three feet up the trunk of the tree. In the latter case boring 
beetles often attack the affected parts of the trunk, as also happens 
sometimes with trees affected by Sphcerostilbe repens. The presence 
of black lines in the roots of tea attacked by Ustulina zonata is 
mentioned by Delacroix and Maublanc (2). 
The presence of black lines in dead rubber wood must not, 
however, be considered a certain sign that Ustulina zonata is present, 
as several of the fungi belonging to the Xylariaceae are of common 
occurrence as saprophytes on dead branches and roots of rubber 
trees, and two of these, Nummularia pithodes (B. and Br.) Petch, 
and a species of Xylaria, have been found by the writer to produce 
similar black lines in the wood. On one occasion this species of 
Xylaria was seen to affect living tissues of exposed Hevea roots 
which had been badly wounded some time previously, possibly 
through being knawed by animals. This fungus had entered the 
wounds, and after setting up decay had advanced into the living 
tissues to some extent, although no serious damage was being done 
It is only when these black lines in the wood and bark are associated 
with an extensive affection of the collar and root system of the tree 
that Ustulina zonata should be suspected. 
Pure Cultures of the Fungus. 
Pure cultures were established from the mycelium present in one 
of the black zones taken from the collar of an affected rubber tree. 
In order to do this, small portions of the black plate were cut out 
under sterile conditions and placed on blocks of Hevea wood in 
culture tubes. In a short time a greyish mycelium began to grow 
from the black mass and spread slowly over the block of wood. 
This mycelium was fine in texture, and remained closely adpressed 
to the wood. At a later stage the mycelium in contact with the 
wood became black, and, together with the mycelium in the super- 
