242 
THE MEDITERRANEAN NATURALIST 
and “ fungus ” and hence so called on account of 
the tliread-like filaments which form one of its 
most prominent characteristics. It infests all 
orders of plant life, attacking in particular the 
potato, onion, lettuce, pea, wheat, and the vine. 
The species which attacks the vine is the Pero- 
nospora viticola. It developes itself on the twigs, 
fruit, and leaves alike, but it is usually on the 
last of these that it first manifests itself. 
It makes its appearance as a whitish efifiore sence 
which developes on the underside of the leaf ac- 
cumulating in the greatest quantity on and around 
the veins, while on the upper side it assumes the 
appearance of yellowish and reddish-brown spots, 
that impart to the leaf a faded and mottled 
aspect. A leaf thus affected gives forth a charac- 
teristic fetid odour when rubbed between the 
fingers. 
The fruit is attacked by a similar efflorescence 
which destroys the bloom, and accumulates in 
such quantities around the peduncle, as to absorb 
all of the fluids of the grape, thus retarding their 
growth and causing them to rot away, and fall off. 
When examined under a microscope of a mode- 
rate power the fungus will be seen to consist of 
a network of ramifying threads, which cross and 
recross one another, entering into and entwining 
themselves among the intercellular spaces of the 
leaves, and giving forth a perfect forest of prehen- 
sile threads which stand forth at right angles 
from the surface, and which bear at their extre- 
mities enormous numbers of minute ovoid and 
rounded bodies called spores. 
This vegetative system of ramifying threads, with 
its concomitant spore-bearing filiaments is known 
as the mycelium, and it is within it that the spo- 
res, by means of which the disease is propagated, 
are generated. 
Within the tissues are certain cellular bodies 
known as the oogonia and the antheridae contain- 
ing a granular protoplasm or formative fluid and 
having a presumed sexuality. The oogonia are 
the female organs, and the antheridae are the 
male and by them are produced the oospores , 
which are afterwards developed in the mycelium. 
The oospore consists of a membranous sac contain- 
ing a thin fluid matter. It is of a rounded form, 
and as it is developed in the greatest numbers in 
the autumn, it is commonly known as the autumn 
spore. They are to be seen on the threads of the 
mycelium, and as they have great resisting powers 
to heat, cold, and wet they often remain dormant 
and unhurt for many months after the death of 
the plant to which they owe their existence. 
Humid conditions and a high temperature are 
highly favourable to their development, and it 
therefore follows that they are most active during 
the Spring and Autumn and that during the 
Summer and Winter they are practically quiescent. 
Rain, dew, fog, and hail, greatly assist also, but 
the most potent factor in this climate is the humid 
unwholesome Sirocco. Badlydrained lands, clayey 
soils, and the proximity of springs also play an 
extensive part in fostering the fungus. 
With the return of Spring the oospores become 
once again active and under the combined influence 
of heat and damp they generate the conidia or 
summer spores. These conidia are oval bodies, 
which are developed in the mycelium and are 
given off from the extremities of the branchlets. 
They are so exceedingly small that it would take 
one hundred million of them to cover a superficies 
of one square inch. 
They are generated very rapidly, and being 
easily detached they are wafted to great distances 
by the wind, and, as every spore is capable of form- 
ing a separate vegetative system or fungus, the 
rapid manner in which the disease has spread in 
these islands will be at once understood. The 
Scirocco plays a double part in the propogation of 
the spores. Its warmth and damp favour the 
generation of the conidia, while its movements 
disseminate them over the islands. 
It is to its influence, combined with the except- 
ionally wet conditions that prevailed during the 
months of May and June, when 3 . 2*2 inches of 
rain are recorded as having fallen, and the abnor- 
mal rainfall of July when 3 inches fell, that we 
may largely attribute the present deplorable state 
of our vines. 
The action of this fungus on the vine is most 
demoralizing. It paralyzes the respiratory func- 
tions of the plant, and by absorbing its nutritive 
juices, it devitalizes it. 
From this brief notice of the causes, effects, na- 
ture, and conditions most fovourable to the 
propagation of the disease I shall now pass on and 
briefly'consider the methods of treatment that have 
