Disease of Olive and Orange Trees. By W, G. Farlow, 119 
pretend to say that what Tulasne saw was not a membrane of 
vegetable substance — a part of the fungus itself; but in the 
Californian specimens we had something which looked very much 
like the mm. of Tulasne's figure, and in this case we have satisfied 
ourselves, by observation and experiment, that it is of animal 
nature, and not a part of the fungus, which, instead, was growing 
upon it. It is a little difficult to understand, from what is already 
known of the development of fungi, how any fungus could begin as 
a very thin membrane, composed of small cells filled with oil. The 
initial stage of fungi, if we except the Myxomycetes, as far as we 
know, is filamentous, not membranous. 
The result of our examination of the diseased orange and olive 
leaves is briefly as follows : The disease, although first attracting 
the eye by the presence of a black fungus, is not caused by it, but 
rather by the attack of some insect, which itself deposits some 
gummy substance on the leaves and bark, or so wounds the tree as 
to cause some sticky exudation, on which the fungus especially 
thrives. It is not denied that the growth of the fungus greatly 
aggravates the trouble already existing, by so encasing the leaves 
as to prevent the action of the sunhght ; we only say that, in 
seeking a remedy, we are to look farther back than the fungus 
itself — to the insect, or whatever it may be, which has made the 
luxuriant growth of the fungus possible. With regard to the 
fungus, we are able to assert that it is the same on both olives 
and oranges — the species described by Berkeley and Desmazieres 
under the name of Gapnodium Gitri, which seems to us, together 
with the pycnidial state described by Montagne under the name of 
Antennaria elseojohila, to be but two states of a species identical 
with that described by Tulasne as Fumago salicina. It remains 
yet to find the asci on olives or oranges, which will probably be 
accomplished without difficulty in California. The earliest stages 
of the fungus should be studied by some one living near orange 
groves ; for, although the disease has been known to attack green- 
house plants, it is not very common or, in that case, so favourable 
for study. Especially is it to be desired that careful notes of the 
extent and manner of appearance of the disease, and the climatic 
and hygrometric conditions attending it, should be carefully re- 
corded. 
As a remedy, alkahne soaps, as strong as the trees will bear, 
will no doubt prove advantageous in case of the oranges ; but in 
the case of the olives, much less good is to be expected, owing to 
the presence of the stellate hairs on leaves and twigs. With this, 
our notice of the disease from a botanical stand-point ends ; and we 
commend the subject to the attention of entomologists. — Bulletin 
of the Bussy Institution. 
VOL. XVI. 
K 
