In their wild state the various species of native grapes seem adapted to a great diversity of soils and conditions. But under successful cultivation varieties of the several species are confined to somewhat restricted regions and even localities. Often a grape variety will succeed on one shore of a lake or river and not on the other; on one slope of a hill but not another. It is difficult to point out the determinants of successful grape culture. Adaptability can be known positively in many cases only by trial; for neither conditions of soil, nor climate, nor lay of land determines with certainty the adaptability of a given locality. Oftentimes one variety of a species may not be successful while another is completely so. Many varieties reach perfection in one region or locality but not in another though the conditions may seem very similar. So great is the influence of local environment, oftentimes, that a variety grown in one locality might not be recognized as the same grape when produced under other conditions. The chief natural factors which govern the distribution of varieties of grapes are: Latitude and altitude; temperature of air and soil; water supply; the chemical and physical properties of the soil; air currents; and insects and fungi. Latitude and altitude very largely determine the annual temperature, the amount and intensity of sunlight, and the length of the growing season--all very important factors in growing grapes. Species and varieties of grapes are usually adapted to regions having about the same latitude; northern types do not succeed in the South nor the reverse. Length of season has more to do with the adaptation of grapes than the degree of heat or cold, for some southern sorts are hardy in vine in the North but the seasons in the northern latitude are not sufficiently long for the fruit to mature. On the other hand, northern varieties mature too quickly in the South and pass through maturity to decay with too great rapidity. The metes and bounds of latitude are often set aside in grape-growing by local modifications. Thus it often happens that valleys in regions not generally adapted to viticulture are so protected from cold winds, so open to sunshine, or are so free from fogs or frosts as to furnish ideal conditions for grape-growing. Probably the chief factor in determining the adaptability of a region to grape culture is temperature. Each of the different species and varieties of grapes requires a certain amount of warmth for its best development and can endure but a certain degree of cold. The temperature of a region is chiefly determined by latitude, altitude and proximity to large bodies of water, though variations in the surface of the country are often important modifying agents of temperature and especially influence spring and fall frosts.