This native fungus that causes blight in the hazels is but one of a large number of similar maladies which have appeared and often worsted the horticulturist, in his endeavor to introduce and cultivate foreign species and varieties of plants, and like the tropical fevers, they may pass unnoticed among the natives, but are terribly fatal to immigrants from cooler climates. The disease so well known as the black knot (_Otthia morbosa_, Schu.), and widely destructive to the European varieties of the plum, and Morello cherries, has existed for ages among our native plums and black cherries, doing comparatively little harm; but it seems to protest, by its virulence, against the introduction of some foreign species. The same is true with various blights and rusts which attack the exotic pear, apple, quince, peach, and other of the larger fruits, and we have only to ascend the scale a few degrees from the microscopic fungi to the microscopic insects, to meet on the very threshold of this realm the minute but unconquerable grape louse (_Phylloxera vastatrix_), which for more than two centuries has prevented the successful cultivation of the European varieties of the grape in the open air everywhere east of the Rocky mountains in North America; although this minute insect has ever been present and a constant parasite of the indigenous species of the grape, but scarcely affecting the health of its host. The plum curculio, chestnut and hickory weevils, bean weevil, and many other similar species of insects appear to be ever protesting against the introduction of exotic plants, as well as the improvement of our indigenous kinds. It is this blight, and nothing else, that has prevented the extensive cultivation of the improved varieties of the European filbert and hazelnut in this country, and not the uncongenial soil and climate, as has been so often "officially" proclaimed by men whose theories are far greater than their practical knowledge of such subjects. Men whose experience with these nuts has been limited to a few isolated bushes or trees in gardens or nurseries, where they were protected, or beyond the reach of the spores of the blight fungus, as has already been noted in the experience of Prince, Downing, Barry, and my neighbor Butler, of Brooklyn, could scarcely understand why others should remain so indifferent to such a promising industry, or why the demand for the trees remained so limited, with scarcely an attempt to plant filbert orchards anywhere in this country. Nurserymen have continued to offer the choice varieties at low prices per plant, and to advise their customers to cultivate filberts extensively, even to setting them in hedgerows; and yet home-grown filberts remain as rare in our markets as they were a hundred years ago, and all due to the simple reason that the insidious filbert blight still scatters its spores unrestrained.