34 i HKPOiri' i>K OFFICE OK KXl'EKIMKNT STATIONS. 



C. — Li^lil iiiul licnl-Coiitimu'd. 

 (CO How modil'UMl : Hy 

 ((/) Color. 

 (?>) Kviiporatioii. 

 (<!) Top()j,'i-ii|)hy. 

 (r/) Cliaractor of soil. 



(c) Cultivation. 

 (H HolliiiK. 



(ff) Thickness of planting. 

 (h) Ferniontation. 



(/> Artificial moans — screens, electricity, artificial heat. 

 D.— Air. 



(1) Function above ground. 

 («) Oxygen. 



(h) Carbon dioxid. 



(2) Funi-tiun in soils. 

 (e) Oxygen. 



(d) Nitrogen. 



(e) Removal of carbon dioxid. 



(3) Processes of soil ventilation. 



(f) By diffusion. 



(ff) By expansion and contraction of air due to temperature. 

 (7j.) By exi)ansion and compression due to barometric ]>ressure. 

 (i) Suctional effect of gusts of wind. 

 ij) Air absorbed by rain water. 



(/r) By removal of water through drainage, evaporation, and trans- 

 piration of plants. 

 E. — The soil — function of the soil. 



(1) As rootholds and mechanical supports of plants. 



(2) As sources of plant food. 

 F. — The soil — origin. 



(1) Disintegration and decomposition of rocks. 



(2) Erosion, transportation, and deposition of sediment (by water and 



ice). 

 (.3) Sorting out of sand, silt, and clay by running water and deposition 

 of soils of different texture as a result of sorting. 



(4) Movement of soils by wind. 



(5) Decay of animal and vegetable materials. Humus. 

 G. — The soil — physical composition. 



(1) Solid matter: Mineral, organic. 



(2) Liquid matter: Impure water or soil solution, air. 



(3) Gaseous matter: Carbonic-acid gas, water vapor. 



H. — The soil — kinds of soils: Peat, muck, clay, loam, sand, gravel, stony soils. 



I. — The soil — texture of soils: Relation of texture to air, retention and move- 

 ment of water, drainage, temperature, weight, iind solidity, roothold of 

 plants. 



J. — The soil — plant food in the soil and air (general survey). 



(1) Elements essential to plant life. 



(2) Elements found in minerals. 



(3) Elements and compounds in air (oxygen, nitrogen, carbon dioxid, 



ammonia). 



(4) Elements in water (hydrogen, oxygen, and dissolved oxygen). 



