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 <WSD>tissue</WSD> powder , or mouse liver powder did not further improve the specificity of staining . 
Meaning of the word marked with <WSD> tags:  part of an organism consisting of an aggregate of cells having a similar structure and function