PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 243 



Another crop that is largely determined by climate is the 

 sugar beet. The beets will grow well in a warm wet climate, 

 but the sugar content will be high enough to warrant growing 

 them commercially only in a cool region and where the hours 

 of daylight are many. This crop has made its best development 

 commercially, in the United States, not for from the isothermal 

 line of 70°. 



The United States Department of Agriculture, through the 

 Office of Farm Management in cooperation with other branches 

 of the Department is now studying in great detail the geo- 

 graphical and climatological distribution of the various farm 

 crops in the United States. The charts and tables will include 

 many phases of climate, crop distribution, dates of planting and 

 harvesting, crop yields, etc. When this is completed it will un- 

 doubtedly be one of the most important contributions to agricul- 

 ture ever made. 



CRITICAL PERIODS OF GROWTH 



Experiment Station investigators have found that every 

 plant has its optimum temperature and moisture values during 

 which it makes its best development, that this varies in different 

 periods of growth, and that the heat and moisture must be in 

 right proportion. 



The plant food is brought to the roots of a plant by the 

 moisture in the soil there to be worked into vegetable tissue by 

 the energy of the solar rays. If there is a lack of plant food 

 part of the solar energy is wasted, while, on the other hand, if 

 there is more food brought to the roots than the solar energy can 

 utilize then the food material is wasted. 



In the arid districts of the western part of the United States 

 there is naturally too much energy for the food supply, but when 

 through irrigation a large amount of fuel is made available for 

 the great solar engine, remarkable crops result. 



In the highest latitudes there is generally an excess of 

 moisture and a deficiency of heat. These are the conditions that 

 prevail in much of northern Europe, and there the crop yields 

 are largely a question of temperature variations. 



In some places where the rainfall is sufficient but the tem- 



