Sentence:  To summarize the purpose of the Skeletal Maturity Chart : each contains two kinds of skeletal maturity norms which show two quite different methods of depicting developmental level of <WSD>growth</WSD> centers . 
Meaning of the word marked with <WSD> tags:  (biology) the process of an individual organism growing organically; a purely biological unfolding of events involved in an organism changing gradually from a simple to a more complex level