BULLETIN OF THE BUSSEY INSTITUTION. 405 
those who have formed any opinion on the subject, as a fungus. We 
have received, at different times, from California specimens of leaves 
and stems of orange and olive trees covered with the black growth, 
and have been able to study the fungus, which presents some points 
not without interest in a botanical point of view; and, if our conclu- 
sions do not point to a direct remedy, it will be conceded, we hope, 
that we have contributed towards removing some misconceptions as 
to the nature of the disease. At this distance, remote from all oppor- 
tunities of observing the disease on living trees, there are, of course, 
some points in the development of the fungus which we have not been 
able to study; and our correspondence has not been sufficiently ex- 
tensive or minute to enable us to give any statistics of the ravages of 
the disease, to ascertain the climatic or other changes which have pre- 
ceded or accompanied the breaking out of the epidemic, or to decide 
whether it is the same form of disease which has been reported to 
occur in Florida. Our specimens present the disease as it appears 
when in a somewhat advanced stage, and after. the leaves and stems 
have become so changed as to attract attention. 
Mycevium. — The leaves of the olives which are affected by the 
disease are somewhat curled and shrivelled, and are of a browner color 
than normal leaves which have been gathered but a few weeks. On 
both surfaces of specimens sent us are black spots of greater or less 
extent, but in no case is the leaf perfectly black. On the upper sur- 
face the black spots are more numerous, more distinct in outline, and 
harder in substance, than on the lower, where they were more diffuse 
and of a powdery consistence. ‘The twigs, of which we received only 
small specimens, are covered with spots which resemble more closely 
those on the upper than on the lower surface of the leaves. In one 
specimen the spots are nearly confluent, and the bark is visible in only 
a few places. After the leaves or stems have been soaked in water 
for a short time, the black substance can be scraped off without the 
least trouble, leaving the bark tolerably clean. The black substance, 
when seen with a magnifying power of four hundred diameters, is found 
to be composed of the stellate hairs peculiar to the olive, over which is 
growing a fungus, to the dark color of whose mycelium the spots owe 
their color. The mycelium is very variable in appearance. As a 
rule, it is composed of moniliform hyphz, whose cells are .006 mm. 
by .008 mm., and in some places almost spherical. The color of the 
