Clay Loam 



Soil material that contains 27 to 40 per cent of clay 

 particles and 20 to 45 per cent of sand, the rest of silt. 



Claypan 



A layer of compact and relatively impervious clay, not 

 cemented, but hard when dry and plastic or stiff when wet; 

 similar to a true hardpan in that it may interfere with the 

 movement of water or with the development of roots. 



Clean Tillage 



Cultivation of a field to prevent the growth of all plants 

 except the particular kind of crop wanted. 



Clear Cutting (Felling) 



The felling of all merchantable trees in an area in one 

 operation, cf. Selective cutting. 



Clearing 



(1) An area of land from which trees and shrubs have 

 been removed. (2) One of the steps in the preparation of a 

 tissue for microscopic observation. 



Cleistogamous 



Refers to Self-pollination (q. v.) in flowers that do not 

 open, e.g., some violets. 



Climacteric 



A great change in a physiologic process, e.g., a pro- 

 nounced rise in the respiration rate at about the time that 

 some fruits such as the apple are picked, or the menopause 

 in human beings. 



Climagraph 



See Climograph. 



Climate 



The aggregate of all atmospheric or meteorological influ- 

 ences, principally moisture, temperature, wind, pressure, and 

 evaporation, which combine to characterize a region, cf. 



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