Sentence:  Two absorptions of * * f with ethyl acetate or two absorptions of * * f ( which had been passed through Dowex-2-chloride ) , NS and * * f with crown gall tissue powder , or mouse liver powder did not <WSD>further</WSD> improve the specificity of staining . 
Meaning of the word marked with <WSD> tags:  to or at a greater extent or degree or a more advanced stage (`further' is used more often than `farther' in this abstract sense)