In treating of the following injurious fungi only such facts in regard to their manner of growth are mentioned as is necessary to enable one to apply intelligently the given remedies. A few preliminary remarks therefore concerning fungi as a class will be useful.

First, fungi are true plants which originate from spores, often of more than one kind, which answer the purpose of seeds, but which are much simpler in structure. Where no spores are present therefore no fungus or fungus disease can appear, any more than weeds can grow where no seeds have been allowed to ripen. Fungi however produce spores eyen more abundantly than weeds produce seeds, and there is hardly a locality in which fungus spores of some kind are not present. Many fungi however are limited to particular localities, and spread to other regions only when the spores are accidentally introduced, or when the plants upon which they live are introduced for cultivation. Thus the grape rot, which is common through the Eastern States, is still unknown in many parts of the country, and it has but recently been accidentally introduced from this country into France, where it threatened, until checked by artificial remedies, to seriously interfere with grape culture in that country. Many similar examples could be given.