The spelling of the name is a bit of a discussion. If we take it that
Gagnepain named it because the leaves look like that of a Viola species,
then the correct name is T. violaefolium......... So that's a third
alternative. And that is probably the correct one, since that is how
Gagnepain published it in the first place. There has been some discussion on
whther the name would be derived from "violius" but that I never understood.
So, let's try (incl. myself) to stick to T. violaefolium.