Sentence:  If , in a certain part of the range , it starts life 1 foot longer than do any of the other ( relatively <WSD>large</WSD> ) giants , and reaches maturity at , let us guess , 18 inches longer than the others , a quadrupling of the maturity length would result in a maximum of ( nearly ) 40 feet . 
Meaning of the word marked with <WSD> tags:  above average in size or number or quantity or magnitude or extent