This descent from an original species with plants changed by environment has given us, in America, types of the wild grape as widely diverse as the regions they inhabit. The species found in the forests have developed long slender trunks and branches in their struggle to attain sunlight and air. At least two species are dwarf and shrubby, or infrequently climbing, two to six feet high, growing in dry sands, on rocky hills and mountains where roots must cling to rocks and penetrate into interstices. Still another form runs on the ground and over low bushes and is nearly evergreen, but in the herbarium can hardly be distinguished from a grape whose habit of growth is strikingly different. Some are long-lived, growing and bearing fruit for two or more centuries, while others reach no greater age than the ordinary shrub. Some have enormous stems, a foot or more in diameter, gnarled and picturesque and supporting a great canopy of branch and foliage,[38] while others are slender in stem and graceful, almost delicate, in character of vine. Not less remarkable than the differences in structure is the adaptability of the genus and some of the species to varied climatic conditions. Several of the wild grapes develop full size and display natural luxuriance and fruit-bearing qualities only in the Middle States, but may be found on dry, gravelly, wind-swept hills far to the north or in some hot and humid atmosphere of the South, as if to show indifference to wet or dry, heat or cold. On the other hand there are many strong points of resemblance between the score or more of species. The organs and characters that do not bear the strain of changed environment, nor suffer in the perpetual warfare of nature, are much the same in all of the species of Vitis. Thus the structure of flowers, fruits and seeds is practically identical; all have naked-tipped tendrils; leaves and leaf-buds are very similar; and the various species usually hybridize freely. They are alike in the unlikeness of individual plants in any of the species; that is, all of the individuals of the genus are most variable and seeds taken from the same vine may produce plants quite unlike one another and quite unlike the parent. These few facts regarding the evolution and distribution of American grapes lead to two important conclusions: