Some plants seem to be able to adapt themselves to any climate and therefore are born explorers, but the greater number are too fastidious regarding conditions of soil, heat, light and moisture to thrive well everywhere. It is a noticeable fact that the most successful plant invaders usually come in the wake of human colonizers and stick to the sphere of man’s influence. For example, the Butter-and-Eggs (_Linaria Linaria_) has followed the railroad tracks almost entirely over the tropical and semi-tropical world. Sometimes, however, hardy plants advance into the primeval jungle, there to give battle to its lusty inhabitants. On the whole, annuals have a better chance than perennials to gain a foothold in a new country. Every spring the weeds, grasses, and common flowering plants have to start all over again from a seed beginning. The spores of newcomers, therefore, have almost an equal chance with the established inhabitants. On the other hand, the bodies of perennials occupy the land in close-packed ranks all the year, ready to dispute every inch of ground with an aggressor. It is very hard for new plants to gain entrance into a well-grown forest. Man has been of tremendous aid in the distribution of plants over the earth’s surface. Either consciously or unconsciously he takes his plants with him wherever he goes. It was the Emperor Chang-Chien who carried the Bean, Cucumber, Lucerne, Saffron, Walnut, Pea, Spinach and Watermelon from Asia to China about 200 B. C. The period of Roman conquest was a great epoch in the history of plant migrations. The Peach and the Apricot first became prominent as fruits at that time. Roman generals introduced the Pear, Peach, Cherry, Mulberry, Walnut and many ornamental shrubs into England. From an obscure native of Bengal, the Sugar Cane has become an important plant of wide distribution. Coffee, a wild berry of Arabia, is now the chief crop of whole countries in the West Indies and South America. The yellow Maize of America has become a citizen of the world. The weak and humble Wheat is the sole possessor of thousands of square miles of land in America, Russia and elsewhere. All this has been wrought by man’s efforts. When it is to his interest, he fights the battles of plantdom, and because of his superior knowledge and equipment is of tremendous service. Sometimes, however, he gives aid to his plant friends through motives that are quite unselfish. A romantic story is related of a French naval officer named Declieux who once elected to carry a Coffee Plant to the Colony of Martinique. The supply of water ran low during the voyage, and, rather than see the plant die, the man shared his daily glass with it, at considerate discomfort to himself.