THE COTTAGE GARDENER AND COUNTRY GENTLEMAN’S COMPANION, July 28, 1857. 
2G5 
soil saturated with sea water, and those situated in the plains 
of the country from whence I write, where a channel is 
formed between every two rows of Vines, which are frequently 
watered in summer; or, again, between those on the dry 
southern precipices of our steep mountains, ascending to a 
height of nearly a thousand feet. Still in these different 
localities the Vines were in some places spared, in others, 
during the last year, diseased to the total annihilation of 
the vintage, and all of them exhibited during the past May 
and June a diseased growth. Single plants, also, were often 
shown me by the proprietors which the year before were 
diseased to a very high degree, but this year were perfectly 
sound, and the contrary. When, as was the case in some 
peculiarly damp situations, as Murano, the Vines had suffered 
from the influence of exuberant moisture, and their leaves 
had in consequence assumed a yellow tinge, such plants 
were so far from being more palpably affected by the fungus, 
than those which looked perfectly sound and green, that on 
the contrary they were frequently altogether free. These 
circumstances render it altogether improbable that the Vines 
are suffering from a general disease, in consequence of 
which the local morbid phenomena and the fungus make 
their appearance. 
Far less are the Vines affected by a local malady; for, as 
is proved by the phenomena which I am about to relate, the 
fungus does not appear on parts of the plant already im¬ 
paired by disease, but, on the contrary, on perfectly sound 
organs, and the disease of the tissues begins precisely at 
those spots to which the fungus adheres by especial organs 
of attachment. Here, then, the connection is so clear be¬ 
tween cause and effect, between the agency of the fungus 
and the disease of the plant, that the opposite view, which 
is not confirmed by a single positive fact, appears to me to 
be flatly contradicted.* 
The only circumstance which can be adduced in favour of 
the predisposition of particular Vines for disease, and one 
which has been much noticed in Italy, is that certain varie¬ 
ties of Vine are more subject to be attacked than others, 
those, for instance, the skin of whose grapes is soft and the 
pulp juicy, while those with a firmer skin and harder flesh 
are spared. This, however, may be put aside as regards a 
peculiar susceptibility in the varieties just mentioned, inas¬ 
much as the harder grapes, in consequence of the toughness 
of their tissues, present a greater resistance to the attacks 
of the fungus. 
Independently, however, of the question whether the 
Grape disease is the consequence of a general indisposition 
of the Vines, one of great importance arises, viz., whether, 
in consequence of the mildew, the general health of the 
Vines is impaired. This, as said above, was not in the 
remotest degree the case in Italy, but it appears from the 
Journals of last year that in many more southern districts, 
as in Madeira, the Vines perished. It is conceivable, indeed, 
that the attack of the fungus may produce such a disease 
in the bark, and so derange the physiological functions of 
the leaves, that the plant may for a time be prostrated, 
though possibly the notion that the Vine is irrecoverably 
lost may be premature. It is, however, difficult to judge of 
the matter at a distance. 
I proved by experiment during the course of this year, as 
in Switzerland in the preceding season, that the fungus does 
not spread from the Vine to any other plant. Similar fungi, 
indeed, occurred commonly on other plants, as on Roses, 
partly before the Vines exhibited any symptoms of disease, 
but none of these appeared to me to be identical with 
Oidium Tuckeri. 
As regards the connection indicated above of the fungus 
with the cuticle of the green organs, and its power of pro- 
* This notion, that the Vines are diseased only in consequence of the 
attack of the fungus, is most expressly defended in the report of the 
commission appointed by the Venetian Institute, whose reporters were 
Prof. Visiani and Dr. Zanardini (Rapporto della commissione nominata 
dall* I. R. Istituto Veneto di scienze, lettere ed arti per lo studio della 
malattia dell’ uva; in den Atti dell* I. R. Istituto Veneto, &c. Tom. IV. 
Serie II.) It was of immense practical importance to give currency to 
this view, since the proprietors fancied that they had a remedy against 
the disease in cutting the Vines down to the ground, and the consequent 
renovation of the shoots, a process, however, which entailed a certain 
loss for some years. The Venetian Institute therefore received with 
thanks my letter printed in the Official Gazette of Venice of the 1st of 
June of the current year, in which I stated the accordance of my views 
in this respect with those of Dr. Zanardini. 
during disease, if clear notions on the subject are desired ! 
we must not choose for examination those parts which are 
thickly covered with the fungus, but those in which it 
appears under the form of a delicate arachnoid web, scarcely 
perceptible under a lens. It is a matter of indifference, in j 
this point of view, whether the bark of the green branches 
be chosen, the tendrils, the peduncles of the bunches, the 
integuments of the closed flower-buds, or tlie young fruit of 
but one or two lines long, provided the leaves are excepted. 
With respect to the extension of the fungus on its first 
appearance, it must be considered as altogether local, for it ! 
occurs in insulated specks, which send out radiating threads 
from their circumference, and so becoming confluent, gra¬ 
dually cover, more or less completely, the surface of the 
organs which are attacked. On the branches the parasite 
occurs regularly on the lowest and oldest internodes; large 
spots covered with the fungus appear on these, and, at a 
later period, on the intermediate internodes, while the upper 1 
internodes (as is at present universally the case here) are 
altogether free. The fungus often spreads to the ovaries 
from the peduncles, which are already attacked before the 
blossoms expand, since the threads of the Mycelium, a short 
time after the corolla falls, creep over the nectary and in¬ 
volve the berries, commencing at their base. Meanwhile 
new centres of development arise from which the fungous 
web commences, caused probably by the oval vesicles or 
spores, which are produced at a very early period of growth 
upon the erect threads, and which germinate very readily 
and are found widely dispersed over every part of the plant, 
as, for instance, on the ovaries soon after the fall of the 
blossom, and then mixed with pollen grains. 
The threads of the Myceliumt creep constantly in a hori¬ 
zontal direction, adhering most accurately to the cuticle. 
While these are yet at a considerable distance from one 
another (Fig. 1) we perceive that they are branched in a 
pinnate manner; and since these branches are repeatedly 
divided in the same manner, in consequence of their cross¬ 
ing, the whole assumes the appearance of a net, which in a 
short time loses its regularity from the incursion of neigh¬ 
bouring threads. They have in consequence a tendency 
to adhere not only to the matrix, but also to each other 
(Fig. 3) where they cross; so that except strong magnifying 
powers be used, an appearance arises as if the branches 
were far more numerous and irregular than they are in reality. 
In the older portions of the threads which lie in the 
middle of the fungal spots the fructifying branches begin 
to show themselves at a very early period, springing out 
on their upper side in a vertical direction, but not always 
perfectly rectilinear. While the creeping threads are divided 
into long articulations by distant and obscure septa, the up¬ 
right threads are always distinctly jointed. They pass from 
a tolerably cylindrical to a clavate form (Fig. 4.), showing a 
greater quantity of protoplasm in the upper cells, but espe¬ 
cially in the last. This at a later period swells out into an 
oval form, and is separated by a distinct septum, a greater 
or less number of little vacua being first formed in the 
protoplasm (endochrome). During the past spring I found, 
almost without exception, only a single oval utricle at the 
tip of each thread, whereas, in the autumn of 1851, two or 
three were generally present, forming a little necklace. I 
have already remarked in my former treatise that the size 
of these fallen utricles is subject to great variation, and 
must therefore be used with some circumspection in the 
distinction of species. 
The connection of the fungus with the matrix is, as was ; 
before mentioned, of especial moment as regards the theory 
of the disease. To make this connection clear we must 
examine the earliest state of the fungus on the bark of the 
branches and tendrils, or on the young fruit. These organs 
appear, after various degrees of the evolution of the fungus, 
perfectly green, but for the most part numerous brown specks 
t The investigation of the Mycelium must be made with light reflected 
from above, for which purpose nothing is better than Lieberkuhn’s 
mirror. It is self-evident that such spots must be chosen as are pro¬ 
tected from every cause of injury, or otherwise the tender threads will 
infallibly be damaged. It appears probable that this simple and obvious 
precaution has been neglected by Trevisan, who asserts with much ear¬ 
nestness (Sulla origine delle alterazioni che osservansi alia superficie 
delle parti verdi nelle viti affette dal bianco dei grappoli. Osservazioni 
di Vittore B. A. Trevisan, Padova, Ottobre, 1852), that fungi never grow 
on the sound cuticle, but always on already diseased patches. 
