The Audubon Societies 369 



trace the so-called "life-zones," that is, the land areas where crops can be grown, 

 throughout North America, with especial emphasis upon the arrangement of 

 those zones in the United States. Bulletin No. 10, by Dr. C. Hart Merriam, 

 published in i8g8 by the U. S. Department of Agriculture (Division of Biological 

 Survey), contains a map of the United States upon which these life-zones are 

 traced in color, and on which the humid and arid portions of them are also 

 indicated. 



We find three great divisions of temperature: cold (boreal) in the North, 

 and high up along mountain-ranges even into Mexico; temperate (austral) 

 throughout the United States and Mexico, except on the cold mountain heights 

 or in the hot lowlands; and hot (tropical) in southern Florida, the edges of 

 Texas, and Southern California, the tip of Lower California, and m;)st of 

 Central America, with a part of Mexico. 



Within these regions of heat, cold, and partial heat and cold, only certain 

 kinds of vegetation will grow or particular forms of animals thrive. To the 

 far North there are almost endless stretches of ice and snow, along the southern 

 limit of which, during midsummer, the temperature rises to about 50° Fahr. 

 Below this frigid zone, which may be described as Arctic-Alpine, and where no 

 trees can grow, and only a few rugged, dwarfed plants, beautiful beyond de- 

 scription during the period of bloom, comes a broad transcontinental belt of 

 evergreen (coniferous) forests that bears the name of the great bay, the southern 

 shores of which it only partially surrounds, namely the Hudsonian Zone. Here, 

 also, it is too cold to raise any but the hardiest crops. Indeed, in a climate 

 where the highest summer temperature is only a little over 57'^ Fahr., one would 

 hardly expect to find crops of any amount or value. So, vast as the land-area 

 in these zones may appear on the map, they are as yet of little value to man in 

 producing food-supplies beyond fish or wild game, and these only in limited 

 quantity. The great Canadian Zone, which forms the extreme southern part 

 of the Boreal Region, except along mountain-heights farther south yet, is 

 where we may begin a survey of agriculture. Before making a list of the dilTerent 

 kinds of food-supply found in this zone and the more temperate ones, it will 

 be helpful to make a simple study of the kinds of soil in which crops grow. So 

 important is this matter of soils that the U. S. Department of Agriculture has 

 a special staff of workers whose business it is to chart different kinds of soil on 

 large colored maps. You will find it interesting to look at such maps, where the 

 prominent feature is the soil. Here you will imd the location of swampy areas, 

 tidal marshes, coastal beaches, meadows, muck-beds, rough stony land, tine 

 sandy or gravelly loam or varieties of these types of soil. On page S42 in Mrs. 

 Anna B. Comstock's 'Handbook of Nature-Study,' you will discover a heljiful 

 method of becoming acquainted with the earth beneath you, and if you will, in 

 addition, bring from your own home grounds a few handfuls of earth to compare 

 with samples which your state boards of agriculture will doubtless be glad to 

 loan or give you, in a short time you will bi- able In tell one soil from another. 



