“Mildew” is just one of those loose terms which represent no definite idea, or a very different one to different individuals. Talk of _mildew_ to a farmer, and instantly he scampers mentally over his fields of standing corn in search of the brown lines or irregular spots which indicate the unwelcome presence of _Puccinia graminis_, known to him, and to generations of farmers before him, as “mildew.” Try to convince a Norfolk farmer that anything else is “mildew,” and he will consider you insane for your pains. Speak of _mildew_ in your own domestic circle, and inquire of wives, or daughters, or servants, what it means, and without hesitation another, and even more minute species of fungus, which attacks damp linen, will be indicated as the true mildew, to the exclusion of all others; and with equal claims to antiquity. Go to Farnham, or any other hop-growing district, and repeat there your question,—What is _mildew_?—and there is every probability that you will be told that it is a kind of mould which attacks the hop plant, but which differs as much from both the mildew of the farmer and the laundry-maid as they differ from each other. The vine-grower has his mildew, the gardener his mildewed onions, the stationer his mildewed paper from damp cellars, the plasterer his mildewed walls, and in almost every calling, or sphere in life, wherever a minute fungus commits its ravages upon stock, crop, or chattels, to that individual owner it becomes a bug-bear under the name of “mildew.” Reluctantly this vague term has been employed as a portion of the title to this chapter, but it must be limited in its application to the “mildew of corn,” known to botanists as _Puccinia graminis_, and _not_ to include the numerous other microscopic Fungi to which the name of _mildew_ is often applied. The origin of this term and its true application may undoubtedly be traced to _mehl-thau_, “meal dew.” A singular proof of the ignorance which prevails in regard to all the fungal diseases of corn, may be found in the fact that at least one of our best etymological dictionaries states that the _mildew_ in corn is the same as the _ergot_ of the French. Had the writer ever been a farmer, he would have known the difference; had he ever seen the two, he could scarcely have made such a mistake. It is barely possible for him ever to have heard the ergot of grain called by the name of _mildew_.