Circumboreal 



Refers to organisms occurring in North ' America and 

 Eurasia. 



Circumpolar 



Refers to organisms that occur in the polar regions of 

 both hemispheres. 



Cirque 



A deeply eroded depression with steep slopes in areas 

 which have been glaciated, syn. Corrie. 



Cladode 



See Cladophyll. 



Cladophyll 



A modified stem that has the appearance and the func- 

 tions of a leaf, e.g., asparagus, syn. Phylloclade. 



Clan 



A group of animals that includes several interrelated 

 families, or a group of plants arising from a common pro- 

 genitor such as a group of young plants around the parent. 

 cf. Colony. 



Class 



A unit of classification of organisms, composed of orders, 

 e.g. Monocotyledons, Mammals. 



Clavate 



Club-shaped, larger at one end. 



Clavicle 



A bone in the shoulder girdle of many vertebrates. 



Clay 



(1) Small mineral particles of the soil, less than 0.002 

 mm. in diameter. (2) Soil material that contains 40 per cent 

 or more of clay particles, less than 45 per cent of sand, and 

 less than 40 per cent of silt. 



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