Disease of Rubber caused by Ustulina Zonata. 157 
sometimes becomes exposed by the wearing away of the greyish 
brown film above ; c is a white layer in which the globular perithecia 
(/>) are formed; d is a broader band grey in colour and leathery in 
consistency; and e is the black zone on the under surface, which is 
continuous at the margin with the black zone towards the upper 
surface. The black zones are brittle. The perithecia (p) are 
globose and communicate with the exterior by exceedingly narrow 
channels. The minute black dots seen on the fructification after 
the superficial grey brown layer has been worn away, correspond to 
the ostioles of the perithecia. They are raised very slightly above 
the general level of the surface of the fruit-body and are formed 
before the perithecia are fully organised. Each ascus contains 
eight, black, spindle-shaped spores which are somewhat inequilateral 
(Fig. 4, C). The dimensions of these spores are 28-32/a x 7-10/a. 
There are large numbers of thread-like paraphyses between the 
asci. The ripe spores exude from the perithecia under moist 
conditions. When a portion of a fructification is kept damp in a 
Petri dish, the spores are liberated and look like drops of ink spread 
over the surface. The ascus walls deliquesce before the extrusion 
of the spores from the perithecia as in other members of the 
Xylariacese to which the genus Ustulina belongs; this behaviour of 
the ascus walls is probably an important factor in bringing about 
the liberation of the spores. 
The genus Ustulina is distinguished from other members of the 
Xylariacese which have flat fructifications, by the fact that the 
fruit-bodies are rather soft when young and are covered by an 
evanescent layer which often forms conidia before the elaboration 
of the perithecia below. In the closely allied fungus Daldinia 
concentrica, the superficial layer of the young fructifications does 
not always form conidia, so it is not remarkable to find that the 
formation of conidia by the corresponding layer in Ustulina zonata 
is not constant. 
The species Ustulina zonata was first described under the name 
of Spliceria zonata by Leveille (3) in 1845 from material obtained 
on palms in Java. It has since been placed in the genus Ustulina 
by Saccardo (7). 
Effect of the Fungus on the Tissues of Hevea. 
Wood and bark invaded by the fungus become discoloured, and 
near the margin of the affected tissues conspicuous black lines are 
often present, these being caused by the dense aggregation and 
