708 EXPERIMENT STATION RECORD. 



esses of their formation general octodynaniic and special biological 

 phenomena manifest themselves in accordance with the ph3'sico-geo- 

 graphical types of continental zones. Such are the following types of 

 soils: ^ 



(1) Lateritic soils. These are the soils of the tropical and subtrop- 

 ical regions with alternating wet and dry seasons. 



(2) Atmospheric-eolian soils. Formed of the dust rocks in the 

 central regions of the diii'ei-ent continents under arid conditions. 



(3) Soils of dry steppes or steppes deserts. Being formed of argil- 

 laceous and arenaceous primitive rocks, they are chestnut and fawn- 

 colored. 



(4) Chernozem soils. These occur in connection with the grass 

 steppes or prairies of the temperate or warm-temperate regions. They 

 develop best from argillaceous rocks. 



(.5) Soils of wooded steppes and deciduous forests (gray soils), re- 

 sembling chernozem soils, but differing from them in the conditions of 

 their origin, and in their morphological and other properties. 



(6) Sod soils and podzol soils ' ^\'hich are peculiar to the temperate- 

 frigid zone. They are typically developed under mixed woods and 

 bushes and are ordinarily accompanied by concretions. 



(7) Tundra soils. These are formed from the clays and argillaceous 

 sands of the tundras, in a cold climate with a ver}^ long winter. They 

 are characterized, to a greater or less degree, by being perpetually 

 frozen (the subsoil waters are in a solid state). 



The groups of soils named represent the soil zones or belts into 

 which the surface of the continents may be divided. 



The lateritic soils belong to the coastal zone of tropical and sub- 

 tropical continental regions which is broken and cut up bv seas. After 

 them follow toward the north and south, in the order indicated in the 

 above enumeration, the regions with the other soil types. In the zone 

 of the continental plateaus and the inclosed or partlv inclosed plains 

 of the northern hemisphere — in central and southwestern Asia (China 

 Persia, Arabia, Turkestan), in the Caspian region, in northern Africa, 

 and in the western and southwestern States of North America are found 

 the atmospheric-eolian soils and the soils of the steppes deserts. In 

 the southern hemisphere are corresponding zone soils covering central 

 Australia, inland sections of southern Africa (the countr}- of the 

 Hottentots, the region to the south of the sources of the Zambezi 



^Only the best known types are mentioned here, use being made of the results of 

 fitudies of the natural soils of Russia, Western Europe, of some regions of Central 

 and Southern Asia, of America, etc., partly of Australia, and Africa. 



^Podzol soils are unproductive soils consisting mainly of very tine sand, but contain- 

 ing more organic matter than their color would indicate. They resemble ashes in 

 appearance, hence the name "podzol," which indicates this resemblance. They 

 correspond nearly with the Bleisand of Germany. 



