Beta Ray 



A stream of Beta particles with greater power of penetra- 

 tion in the tissues of organisms than Alpha rays (q. v.). 



B Horizon 



A master soil horizon between A and C Horizons (q. v.), 

 a layer of Illuviation (q. v.) in which materials from overlying 

 horizons are deposited. B! is transitional between A 3 and B 2 , 

 but more like B than A. B 2 is the layer of maximum illuvia- 

 tion especially of silicate clay materials, or of iron and 

 organic materials, or with maximum development of blocky 

 or prismatic structure. B 3 is transitional between B and C 

 horizons, often absent. 



Bicentric 



Refers to a Taxon (q. v.) with two centers of dispersion 

 or evolution. 



Biennial 



A plant that lives for two years, usually blooming and 

 fruiting only in the second year and then dying, e.g. carrot. 



Biflorus 



A plant that flowers in both spring and autumn. 



Bilateral Symmetry 



An organism which can be divided so that each half is 

 the mirror image of the other, e.g., vertebrates, snapdragon 

 flower, syn. zygomorphy. cf. symmetry. 



Binary Name 



See Binomial. 



Binom 



See Agamospecies. 



Binomial 



A name of organisms consisting of two words, e.g., 

 Quercus alba, the white oak; the first name is the genus, the 

 second the species. 



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