Viola (odorata or tricolor)

[Jorge_Stolfi]

I do not know whether the text in the Tractatus provides further details about which particular type of viola is meant.

Sorry if I wasn't clear.  Viola (with no qualifier) was since antiquity the common Latin name for the odorata species only (and maybe for other species that could be confused with it, or for any small purple flower in general).   The derivatives of that word are still used in the same way (with no qualifiers)  in English and most Romance: "violetta" in Italian, "violette" in French, "violeta" in Spanish and Portuguese... 

I don't think anyone would have used "viola" for the pansy in the Middle Ages, since the plants, leaves, and flowers are quite different.    That happened only in the 1600s-1700 after Linné invented the binomial name system, and used Viola for the name of the genus that was defined as comprising both species (and others).

All the best, --stolfi