Race 



(1) Biology. A Population within a species that differs in 

 one or more inherited characteristics from other populations 

 but not sufficiently distinct to rate as a Taxon (q. v.). (2) A 

 rapid movement of the tide through a narrow channel. 



Rachion 



The line where waves break in lakes, the places where 

 wave action and undertow cause the greatest turmoil. 



Rod 



The dose or unit of ionizing radiation absorbed by tissues 

 of an organism, equal to 100 ergs of energy per gram. 



Radiation 



(1) The emission and transmission of energy from a 

 source, e.g., Ionizing radiation (q. v.), solar radiation by 

 electromagnetic waves such as light, x-rays, gamma-rays. (2) 

 See Adaptive radiation. 



Radicle 



The lower end of the axis of the embryo in a seed and 

 which develops into a root during germination. 



283 



