Barogram 



The continuous record made by a self-registering 

 Barometer. 



Barograph 



A self-registering barometer. 



Barometer 



An instrument for measuring the atmospheric pressure, 

 cf. Aneroid barometer. 



Barotaxis 



Response by locomotion of an organism or part of an 

 organism in response to a barometric stimulus. 



Barotropism 



Reaction by growth curvature of a plant or a sedentary 

 animal in response to a barometric stimulus. 



Barrens 



An area in which vegetation is absent or poorly developed. 



Barrier 



(1) A topographic feature or a physical or biological con- 

 dition that restricts or prevents migration of organisms or 

 prevents establishment of organisms that have migrated. 

 (2) A condition that prevents or appreciably reduces cross- 

 breeding of organisms. 



Barrier Beach 



See Beach. 



Basal Area 



(1) The area of the cross section of a tree at height of 

 4.5 feet above* the ground, usually expressed as the summa- 

 tion of the basal area of the trees in a forest in square feet 

 per acre. (2) The surface of the soil actually covered or 

 occupied by a plant, especially the basal part, as compared 

 to the full spread of the herbage; in grassland ecology often 



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