F NEW problems confront the economic geographer with such urgent need for solution as the relationship between the cultivation and distribution of an important crop on the one hand and on the other its physical demands upon the land it, occupies. Upon this problem depends in large part the economic exploitation of our world, whether it concerns itself with agriculture, the mining and winning of raw ores, industrial activity, or the like. Pressing as the problem is at the moment, our exact knowledge of the elements for its solution is correspondingly inadequate; not only because of the multiplicity of the factors that generally affect the distribution of the crop and its yield and quality, but also because of the whole complex of conditions which in this most intimate interdependence and interrelationship are exceedingly difficult to resolve into their several effects. Many investigators in various lands are attacking the problem from different directions, but much still remains to be done before definite knowledge is available as to how cultivation and yield vary with soil, relief, accessibility to water, temperature, precipitation, winds, and so forth. To achieve clarity on these points, not only detailed experimentation in many kinds of fields and over wide areas is demanded, but accurate research and measurements of the most important and effective factors. For isolated minor regions such investigations have been completed in several directions and in a number of countries, just as for diverse larger regions of the world, for example, certain portions of Africa, Australia, the Amazon Valley, the United States, Germany, and northern Sweden, among others. Less satisfactory have been the researches into the potential possibilities for the cultivation of some certain crop. 0. E. Baker has discussed the future possibilities of wheat production, and the International Agricultural Institute of Rome has issued a report of its researches into the present and future possibilities of cotton growing lands. In contrast, the utilization and reserves of minerals such as coal and iron ore, and of water power, have been exhaustively studied by great international congresses. I myself have been engrossed for a number of years with the present and potential production regions of our four common small cereals, but the difficulty of finding means to finance the publication of the results of so extensive and exhaustive an investigation in a small country like Sweden, has been insuperable and much of the material has not been worked over; though they doubtless would be of value for themselves, their greatest significance lies in their indicating the regions within the tropics where possible future cultivation of wheat, rye, barley, and oats might extend the settlement and successful permanent occupancy by the white race of certain favorable equatorial regions. In connection with these researches I have also undertaken the investigation of similar-conditions with regard