• RUBBER ^HEVEA) DISEASES ■ 9 
with the roots of the rubber tree and causes infection. A rubber 
tree in one instance was enmeshed with the roots of three other trees, 
all different species. These facts bear upon the problem of the 
nature and cause of the spread of this fungus on roots and the con- 
sideration of the elimination as far as possible of all stumps and 
trees on plantation sites. The forester is confronted with the same 
problem in the case of parasitic root fungi, but except in the case of 
small planted holdings control measures are not practicable. 
The fruiting bodies of the fungus are among the most conspicuous 
of all tropical species. (PL IV.) Originating as a small knoblike 
protuberence, the fungus develops horizontally into a bracket or 
a semicircular shape. It is from a fourth to half an inch in thick- 
ness at the point of attachment and thins out regularly to- 
ward the margin. In exceptional cases the brackets may attain a 
length of 8 inches and a breadth of 20 inches, but the usual dimen- 
sions are about 3 by 4 inches. The brackets may appear singly or 
in numbers, one above another. They may fuse at the sides, form- 
ing masses along the sides of logs or the roots of trees. There is 
usually a resupinate portion from which the fructifications spring 
and from which smaller brackets are sometimes produced beneath. 
The upper surface is slightly concentrically grooved, with occasional 
fine lines or striae radiating from the point of attachment. The 
lower surface is smooth and consists of a layer of very fine pores, 
scarcely visible to the unaided eye. The most conspicuous visible 
character of the fungus is its brilliant color when fresh. The upper 
surface is a rich red-brown with a buff-yellow margin. As the 
fungus reaches maturity, alternating zones of red, brown, and yellow 
appear, which finally become less conspicuous as the fungus dries. 
When dry it is a more or less uniform yellowish brown or wood 
color, with concentric zones of darker color. The lower surface 
when fresh is a bright orange, which deepens to a reddish brown 
with age. This is more or less permanent in dried specimens, the 
color in old specimens being confined to the mouths of the pores. 
The substance of the context when fresh is firm fibrous and is easily 
broken. It consists of thin-walled Iryphse. The hyphse of the pores 
in cross section give the appearance of a true tissue. This is a 
characteristic feature of the tissues of the group to which the fungus 
belongs and is the reason for the hard, horny, brittle condition of 
the pores when dry. A vertical section through the fungus shows 
two distinct layers. The upper or context layer is whitish yellow, 
the lower consisting of vertical pores at right angles to the upper 
layer, which is reddish brown. The color usually fades in old speci- 
mens from the pore layer, except at the lower surface. S >metimes 
there are more than one layer of these pores. This condition, how- 
ever, depends upon the weather and the exhaustion of the substratum 
and is not typical for the species. When dry the edges of the 
brackets curl downward, and they are very hard and brittle. When 
resupinate, the edges of the broad flat plates curl away from the 
substratum and frequently fall to the ground. 
The fungus is propagated by wind-borne spores and by vegetative 
mycelia in the form of strands or cords ramifying through the soil. 
Conidialike bodies were observed on felted masses of mycelium in 
cavities in decayed wood. 
