1877. ] 
VINES AND VINE-CULTURE.-CHAPTER XII. 
Ol 
to exist for many years previously, although, singularly enough, the American 
varieties of Grapes are but little affected by it. In this country, it has caused 
great destruction amongst Grapes, both in vineries and in the open air, and in 
Vine-growing countries the entire season’s crop is frequently destroyed by its 
agency. 
This mildew appears to the naked eye like a little white powder only, resting 
on the leaves, &c. ; but by the aid of the magnifying-glass, it is seen to be a true 
vegetable parasitical growth, as we see it represented by the accompanying 
figure. It is a most insidious enemy, and requires extreme watchfulness, so as 
to observe its very earliest appearance, in order to check its progress. It vegetates 
very rapidly ; from a small speck, it will in the course of a few days spread over 
an entire house, and if not arrested in its growth,, its roots will have penetrated 
Mildew of Grapes and Oidium Tuciceri, with conidia germinating (x 200 dia.). 
so deeply into the tissues of the affected parts as completely to destroy them. 
The mildew itself may be arrested and killed, but its effects are left, the skin 
or cuticle of the berry being blackened and injured beyond recovery. It seems 
to render the berry incapable of distending further, so that it soon splits open, and 
is of course ruined. The tissues of the leaves are also injured in much the same way. 
As to the causes of the Vine mildew, they are, as in most other diseases, very 
difficult to trace. It is sufficient that it does exist. Certain atmospherical con¬ 
ditions are favourable to its development, as to that of all fungoid growth. There 
is no more fertile source than cold, damp, sunless weather, with a stagnant 
atmosphere, and especially if this is succeeded by bright sunshine. On Vines 
grown in the open air, there is seldom a season that they are not affected to 
some extent, but frequently it occurs so late in the season as practically to do but 
little harm. 
The prevention of mildew ought, if it be possible, to be the chief endeavour 
of all Vine-growers ; and in houses or vineries it may be almost prevented. In 
the open air, it is much more difficult to grapple with. As a stagnant atmosphere 
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