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on the upper surface of the leaf, which gradually increases until the part affected 
becomes brown. By turning over the leaf the fungus will be observed spreading 
and destroying the vitality of the tissue; the leaves ultimately wither, crumble, 
and drop off. 
“This form of mildew appears to be produced by continued dampness, more 
particularly when heavy dews or oceasional rains, accompanied by dull or cloudy 
weather, immediately follow a period of dryness and bright sunshine ; it also 
spreads with greatest rapidity, other cireumstances favorable, in positions where 
evaporation is least active. 
« All varieties of grapes having downy foliage are more subject to this form 
of mildew than are those with smooth and shining leaves. 
“The second general form of mildew is that seen on the upper surface of the 
leaves, giving them an appearance similar to having been dusted with fine flour, 
and which may be brushed off without any apparent marks of injury. Occa- 
sionally this will be observed on the berries in early summer, and may have some 
connection with the rot. 4 
‘“Tts effects are those of retarding growth, and the fruit, and even young 
shoots, in extreme cases, crack open, as is seen in the cracking of the fruit of 
some varieties of the pear. 
“The debilitating effects of dry air and dry soil seem to render vegetation 
liable to its attacks, and favorable to its extension. This form of mildew is less 
frequent and not so injurious on the native species of grape as that previously 
mentioned, and when treating on preventives the first described form will be 
more particularly kept in view. The rot in the berry is, perhaps, the most 
fatal disease in the grape, and one whose origin is yet obscure. It is undoubt- 
edly a fungoid growth, from which fact we may deduce its origin to a disorgan- 
ization of the plant, a weakened vitality, proceeding from one or various causes, 
either immediate or remote from its appearance. 
“I purposely refrain from enumerating any of the many theories that have 
been promulgated regarding this disease, further than to mention that it has been 
noted that where it does exist, it is most persistent and fatal on plants growing 
in soils rich in organic matter, showing that a condition favorable to luxuriant 
growth of plant is favorable to the extension of this disease. 
“Tt is also well known that, in the case of foreign grapes grown in glass 
structures, where all the circumstances of culture are in a great degree artificial, 
the rot is prevented in varieties subject to that disease by withholding water 
during the period of swelling and ripening of the fruit. 
“It is probable that we have not yet sufficiently systematized observations, 
on this dizease to enable us to arrive at an intelligent conclusion as to its cause. 
Diseases of this nature are very often the result of causes affecting the plant 
many months previous to the visible development of the malady ; therefore, re- 
ports upou the condition of the soil or atmosphere at the time of its greatest 
severity should not hold too prominent a place in our conclusions with reference 
to its origin. ' 
‘“‘ Assuming these observations to be in the main correct, we deduce from them 
various practical suggestions, some of which may be briefly mentioned. So far 
as our present knowledge extends, the constitution of the soil, either in its 
chemical or physical condition, or as affected in any degree by culture, exercises 
but little if any influence, either in promoting or preventing mildew on the leaf; 
but, keeping in view the supposition that mildew is the result of weakened vi- 
tality, it is within the bounds of probability that a system of special culture 
may be reached which will fortify the plant against injury from such attacks. 
“The only preventives known are those of shelter from heavy dews or rains, 
either by mechanical or natural appliances, and applications of sulphur and 
other antidotes to the foliage. Experiments havesproved that leaf blights may 
