ganisms by migration as at the present time between Asia 

 and Europe, cf. Filter bridge, Sweepstakes bridge. 



Coteau 



A series of Moraines, a term used in Western United 

 States. 



Coterie 



A closed social group of animals, individuals of which de- 

 fend their common territory against members of other 

 coteries. 



Cotyledon 



A primary leaf of the embryo in seeds, only one in the 

 Monocotyledons, two in Dicotyledons. In many of the latter 

 such as the bean they emerge above ground and appear as 

 the first leaves. 



Cover 



(1) The plants or plant parts, living or dead, on the sur- 

 face of the ground. Vegetative cover or herbage cover is com- 

 posed of living plants, litter cover of dead parts of plants. 

 cf. Basal area. (2) The area of ground covered by plants of 

 one or more species. 



Cover, Vegetation 



The area of ground covered by the sum total of plants 

 in an area. 



Coverage 



The percentage of the area of a community covered by 

 a plant or an animal that is attached to the substratum, as 

 seen from above, cf. Cover. 



Cover Crop 



A crop growing close to the ground for the chief pur- 

 pose of protecting the soil from erosion and also for the 

 improvement of its fertility, between periods of regular pro- 



96 



