Very interesting - thanks very much for sharing, violet_blue!

Acta Botanica Yunnanica is available online, at the link below, but only numbers 1 and 2 for 2003, so far; and for them none of the links (eg. abstract) works - oh how frustrating! :)

Here is a link that might be useful: Acta Botanica Yunnanica

violet_blue,
Do any of the species Viola binchuanensis, V. moupinensis or
V. magnifica have leaves with purple veins, midrib, and petiole?

Kim,
V. moupinensis and V. magnifica don't have purple veins, midrib or petiole.

As to V. binchuanensis, I have never seen it and Prof. Huang's description of it was all in Latin which I cannot read so sorry I don't know.

Dear violet_blue,
Thank you for your helpful reply. I will try to get Prof. Huang's paper and translate the Latin. I photographed a viola in two places in NW Yunnan which had large leaves, and the purple veins I described, with smallish mauve-purple flowers below the leaves (which may have been because it was later in the flowering season and the leaves had grown taller than when they first appear). I have not been able to identify it from the key.