A scientist once visiting in Bulgaria noticed that the peasants in that country frequently lived over a hundred years and, in trying to find out the reason, he discovered that they drank large quantities of sour milk. This is alive with a definite kind of bacterium that is of great benefit to the digestive apparatus, and therefore helps in the prolongation of life. In Bulgaria, in other words, a certain food habit of the people has resulted in a definite prolongation of life and fixes that population as of somewhat different characteristics from people not addicted to sour milk. In Japan a whole race lives largely on fish and rice, and while this is not the cause of their yellow skin, it is almost surely the cause of their generally small stature. Many of the English are tall, light-haired, and blue-eyed people, fond of outdoor life and sports, and among the most highly developed of the peoples of the earth. The climate of that island, their generally large consumption of meat and the outdoor life of so many of them, have resulted in quite definite characteristics that make the typical Englishman an easily distinguishable type. In studying man we are able not only to divide him into such broad divisions as white, black, and yellow races, but due to their particular country or mode of life there are scores of racial subdivisions of these larger categories that everyone recognizes. Such differences are often based on stature, shape of head, mental characters and many others, but those still finer shades of difference between, for instance, a Connecticut Yankee and a plantation owner in the South, are, while noted by everyone, very difficult to accurately describe. In attempting to find such major differences in plants, some structural character that would set off one large group of plants from every other group, the botanist has a harder task than the person studying man. For all those differences of language and mentality that make up such a large part of our common knowledge of the different peoples of the earth are characters that are foreign to plants. We are thus thrown back on structure as the chief way in which plants differ, and because their reproductive organs are their most important ones, and therefore least likely to vary, it is upon certain characters of these organs that all flowering plants have been divided.