Viola (odorata or tricolor)

[Bernd]

Don't get me started on Viola taxonomy, it's a nightmare! 

However, regarding the VM plant, regardless of color, there are only 2 closely related species (disregarding subspecies) that look similar:
V. arvensis
V. tricolor

If the VM text accompanying the drawing is indeed related to those, another Viola similar to odorata due to the author's mistake, or something completely different - we don't know.

The Dioscorides text itself is quite vague about the characteristics of the plant Ion, but it's more likely something related to V. odorata:

Ion has a leaf smaller than cissus [2-210], thinner and darker; and little stalks in the midst (from the root) on which is a little flower, very sweet, of a purple. It grows in shady rough places. It is cooling, so that the leaves (applied by themselves or with polenta) help a burning stomach, inflammation of the eyes, and prolapse of the perineum. A decoction of the purple part of the flower (taken as a drink with water) helps the synanchic [abscessed throat], and epilepsy of children. It is also called dasypodion, priapeion, wild violet, or cybelion; the Romans call it setialis, some, muraria, or viola purpurea.