Sentence:  Scarcity of paper caused many Southerners to adopt the practice of cross <WSD>writing</WSD> , i. e. , after writing from left to right of the page in the usual manner , they gave the sheet a half turn and wrote from end to end across the lines previously written . 
Meaning of the word marked with <WSD> tags:  letters or symbols that are written or imprinted on a surface to represent the sounds or words of a language