20
PLANT DISEASES AND FUNGI.
estimated at about one-sixth of the crop. In Maine the reporter
says: "I call to mind one season when we lost more than half our
crop, about mid-winter, by rotting. The apples began rotting under
the 'scab' spots, and eventually the fruit entirely decayed." This
same "apple scab" is destructive in our own orchards, but to what
extent no one has taken the trouble to inquire; and in the Australian
colonies it is another of the foes with which the cultivator has to
contend.
In countries where the cultivation of the grape-vine is of com-
mercial importance, vine diseases, apart from the Phylloxera, cause
immense injury. The Commissioner of Agriculture in the United
States reports: "In my opinion, which is based upon special reports,
and on other available and trustworthy information, the annual loss
from 'grape rot' during the last ten years, in the principal vine-
growing regions of the United States, has not been less than one-
fourth of the entire crop."2 Again, a reporter from Ohio states that:
"In years past grape rot has destroyed hundreds of tons of grapes
here, so that nearly every vineyard has been dug up. I have seen
the produce of whole vineyards destroyed in three or four days."
And yet this is but one of the many diseases of the vine, and is not
the same with the white American mould which is finding its way
into Europe.
Details are unnecessary of the damage done to other important
crops, which are now matters of history, such, for instance, as the
widely-spread potato disease, of which we have had a plentiful
experience here and in Ireland; of the coffee disease which ruined
the plantations in Ceylon, and brought the planters to despair; of
the disease which fell upon the opium poppy in India, and at once
reduced the area of cultivation; of the damage sustained by the
cocoa-nut palm in tropical South America and the West Indies; and
even of the larch disease, which has long been a terror in Northern
Europe and in Scotland. In all these cases the pecuniary loss must
have been enormous, and more than enough to justify the demand for
a closer and more systematic investigation into the history and
mystery of plant diseases, with a view to their remedy.
At the outset of this inquiry we are met by the general question
of the causes of disease in cultivated plants, and are compelled to the
confession that there are several primary causes, of which parasitic
fungi is but one, although one of the most important. Another is due
2 "Report to Commissioner of Agriculture," Washington, 1886.