Disease of Olive and Orange Trees. By W. G. Farlow. 1 1 5 
mouth ; and slight pressure on the covering glass generally causes 
a fresh discharge. 
So far, we have spoken of the fungus as seen on the olive. 
The orange leaves sent us are also covered with a hlack substance, 
which is not so much in spots as in powdery sheets upon both 
surfaces of the leaves, more particularly the upper. The attach- 
ment to the leaf is by no means as strong as in the olive ; and the 
deposit can easily be scraped off, even without previous moistening. 
In fact, in some places it falls off on the slightest touch. No 
specimens of diseased orange-stems were received for examination. 
A microscopic examination shows why the deposit was more easily 
removed from the orange than the olive leaves. The smooth 
surface of the former gives no permanent attachment to the fungus, 
which, as we have before said, does not penetrate into the interior 
of the cells of the mother plant; while, on the other hand, the 
hyphse wind themselves tightly around the stalks of the stellate 
hairs of the olive, from which they cannot be removed. If the 
fungus should attack both oranges and olives, it is very evident 
why the latter would suffer much more than the former. Apart 
from the absence of hairs, which invariably constitute a large pro- 
portion of the scrapings of the olive leaves, that from the orange 
leaves is precisely identical, — the same moniliform hyphae, bearing 
Macrosporium and Helminthosporium spore-like bodies, the same 
pycnidia and stylospores. Micrometric measurements only confirm 
the identity. On the orange leaves sent me, there is a .greater 
proportion of pycnidia, and a smaller proportion of stylospores, than 
in case of the olive leaves ; but that is of course an accidental 
difference, as the olive leaves themselves vary. On the orange, the 
proportion of Helminthosporium-like spores is much greater than 
on the olive ; but from the facility with which the so-called 
secondary forms of fruit are produced in fungi, and their great 
variability, that is not a fact of any importance; and we can in 
the most decided manner affirm that the fungus is the same on 
both plants. 
The first account of a fungus growing upon orange trees, 
resembling in its habits that received from California, was given by 
Persoon, in his ' Mycologia Europaea,' p. 10, published in 1822. 
His description of the new fungus is very briefly given in the 
following words: Fumago Citri, late eflfusa crassinscula nigro- 
grisea. Provenit in Europa meridionali ad folia Citri Medicse, 
quae ssepe tota induit." Later, Turpin published an account, with 
a figure, of a species which he also called Fiwiago Citri, which 
Montague made the type of a new genus, Capnodium, published in 
the ' Annales des Sciences Naturelles,' 3 serie, tome 11, 1840. Mon- 
tague seems to have had doubts as to the identity of the Fiimago 
Citri of Persoon with that of Turpin. Almost simultaneously with 
