Sentence:  Specific staining by DEAE-cellulose treated * * f and * * f , although clearly distinguishable under the microscope from either nonspecific staining or autofluorescence of cells , was <WSD>not</WSD> satisfactorily photographed to show such differences in spite of many attempts with black and white and color photography . 
Meaning of the word marked with <WSD> tags:  negation of a word or group of words