During the nineteenth and the first part of the twentieth century no detailed statistical studies of vegetation in relation to climate had been devised. The work relating to the two was broad, general and superficial. Climatic formations of the world had been described and classified by plant geographers and early ecologists, as Schimper, Warming, Cowles and others. Work was done classifying regions as xerophytic, mesophytic or hydrophytic, but no methods had been published giving means of ascertaining in more detail the degree of xerophytism, mesophytism or hydrophytism. In 1909, C. Raunkiaer, of Copenhagen, Denmark, published a paper on "Life-Forms and Statistical Methods." This work concerned methods which the author had devised to measure the total climatic influences on plants by means of the plants themselves. It was an effort to apply quantitative methods to plants and to classify them as to life-form. The factor selected by Raunkiaer was the adaptation of plants to the critical season as indicated by the degree and nature of the protection afforded dormant perennating buds. Raunkiaer, in addition to his theory, classified four hundred plants carefully selected from the entire world, fitting each into its proper life-form (as based on the protection of the perennating bud), and called the percentages of the groups of growth forms a world normal biological spectrum. Raunkiaer state that a count of the different kinds of plants according to his classification would indicate the nature of the habitat and give a biological spectrum for it.