It does not follow because a plant is a native of a given country that it can be easily cultivated anywhere in that country, or that its finest cultivated varieties will be hardy. Only a few limited territories (owing to the nature of the soil, climate, and exposure) in Germany (chiefly in Bavaria), and in Kent, Sussex, Worcestershire, and Herefordshire, seem to be really favourable to hop-growing in Europe. Certain parts of the Pacific coast of the United States have of late years proved a very successful ground, although hops were introduced from Europe and first cultivated with considerable success in the State of New York. The same dangers and troubles attend the hop-crop in all these regions. These are blight, red-spider, mildew and mould, besides several less important insect pests. The hop-blight, or “black-blight,” is a plant-louse or aphis (Fig. 55) like the rose-aphis, and does great and increasing damage to the hop-crop in England, destroying the young and tender shoots in the months of June and July. In 1882 the hop-crop was reduced from 459,000 cwt. (of the preceding year) to 115,000 cwt. by this insect, and the wages paid for hop-picking from £350,000 to £150,000. These figures give an idea both of the damage done by blight and of the amount and value of the annual crop, for the mere picking of which so large a payment is made. Red-spider is a small mite or acarid which has done a good deal of damage in Kent. But mildew and mould are more serious. These are due to a delicate, thread-like kind of fungus, which spreads on the leaf. Many kinds are known in various parts of the world and on various plants. They may grow on one kind of plant without doing injury to it, but if they get on to another, cause deadly destruction of the foliage. It was an otherwise harmless mould, or leaf-fungus, which destroyed the coffee plantations of Ceylon. It had lived in the Ceylon forests on other plants without attracting notice; but when the coffee tree was introduced and cultivated in large areas, this little fungus seized on it, grew with terrible activity, and received the name “vastatrix” from the botanists who traced its history, and showed that it was the destroyer of the coffee plantations. [Illustration: FIG. 57.—Ordinary wingless female hop-louse, multiplying parthenogenetically throughout the summer.]