404 BULLETIN OF THE BUSSEY INSTITUTION. 
No. 21.—Ona Disease of Olive and Orange Trees, occurring 
in California, in the Spring and Summer of 1875. By W. 
G. Fariow, Assistant Professor of Botany in Harvard 
University. 
Durine the past summer, numerous complaints have come from 
southern California of a fungus which 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, 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 information 
has been received; but, as in a letter from San Diego, dated June 3, 
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 speci- 
mens 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 color. 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 slightly, but markedly 
injurious; and that, in its advanced stages, there is present on the 
leaves and stems a blackish substance, which is universally regarded, by 
* We are in receipt of a letter from Mr. Cleveland, dated early in January, 
1876, in which he sends specimens of the fungus on orange-leaves, which, he 
writes, is at that time common at San Diego. 
