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II.— On a Disease of Olive and Orange Trees. By W. G. Farlow, 
Assistant Professor of Botany in Harvard University, U.S.A. 
Plate CL. 
Last summer numerous complaints came from southern California 
of a fungus wliicli had attacked the olive and orange trees, and 
which was causing a considerable loss of those two crops. Our 
attention was first called to the subject by Dr. H. W. Harkness, 
who, in a letter from San Francisco, dated May 11, 1875, sent a 
specimen of the fungus on an orange leaf from southern California. 
Of the extent of the ravages of the fungus at that date no in- 
formation has been received ; but as, in a letter from San Diego, 
dated June 3, 1875, Mr. D. Cleveland wrote that there was no 
trace of the fungus in that vicinity, we may suppose that the 
disease first appeared not far from Santa Barbara, where we have 
definite knowledge of its occurrence, and where great damage was 
done later in the summer. In a letter from Dr. George Thurber, 
dated September 20, enclosing some specimens of the fungus, is the 
following from a correspondent in Santa Barbara : " We are troubled 
with our olive, lemon, and orange trees. A small fungus appears 
on the leaves, twigs, and branches, at first visible only with a 
microscope, and of a green colour. As it increases in size it turns 
brown, and then black. The olive is so exhausted that it is unable 
to fruit. The orange and lemon stand it better, but their fruit is 
so inferior as to be practically worthless." On the day of the 
receipt of Dr. Thurber's letter, another was received from Professor 
Dana, also enclosing specimens from Santa Barbara. 
From the general tenor of letters from California, it is evident 
that, if this is not the first year of the appearance of the 
disease, it is, at least, the first in which it has attracted general 
attention; that its effect on the olive and orange crops has not 
been shghtly but markedly injurious; and that, in its advanced 
stages, there is present on the leaves and stems a blackish sub- 
stance, which is universally regarded, by those who have formed 
any opinion on the subject, as a fungus. "We have received, at 
different times, from Cahfornia 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 
conclusions do not point to a direct remedy, it will be conceded, 
we hope, that we have contributed toward removing some mis- 
conceptions as to the nature of the disease. At this distance, 
remote from all opportunities 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 
