Sentence:  Sections of sweet clover stem and root tumors were treated with 1 : 10 solution of * * f for 30 minutes , washed in buffered <WSD>saline</WSD> for 15 minutes , stained with * * f for 30 minutes , and washed for 15 minutes in PBS . 
Meaning of the word marked with <WSD> tags:  an isotonic solution of sodium chloride and distilled water