Underscore in XProc version

[LucasHorseshoeBend]

Compare the extract of the Word version of file 57-03-05

with the representation in https://vmcp.rbg.vic.gov.au/text/letters/1850-9/1857/57-03-05-final

I can fix the indents by replacing with tabs if necessary, but the underlines are important to show the logic of the arrangements, as they are Mueller's indication of the plant families

The proper structure is evident in the XTF version

I have NOT checked for other instances where underlines have not been represented in XProc, but I assume it is a general issue.