I agree, not necessarily medicinal. I think they could be meant to indicate fast growing edibles that would also keep soil from eroding after a catastrophic flood or other event which might affect the food supply. Recently, three locust plagues in three different countries came across my feeds, that would also qualify.
I was thinking about Viola arvensis, it is similar to Viola tricolor but is larger, has more seeds, larger sepals, and lighter coloration. The latter two attributes seem to match the vms viola. I once had a Viola tricolor or arvensis growing near my house, don't know for sure which species, gave it some fertilizer and it grew really long, and lasted through the winter, under the snow, in fact the entire plant stayed green the whole time as well and then continued to grow the next year (they are supposed to be annuals, we are in zone 4) They grew really long, about two feet, kind of sprawled around. Maybe hardy hybrids are involved. I do prefer the taste of our local V. tricolor, has a wintergreeny aspect absent in the other violas that grow nearby (heart shaped leaves).
There are so many violas, and so many waterlilies. They might be indicating groups of plants, especially since they probably did consider many that we currently differentiate to be the same, and or there might not have been as many varieties in the past.
I agree the flower of the waterlily seems most to resemble Nymphoides. But when i see the rhizomes they are generally of the tropical banana type, or just tangled roots. The rhizome drawn seems more like Nymphaea
Maybe they saw the Nymphoides flower, dug up a nearby rhizome with a similar leaf, not realizing it was a Nymphaea that hadn't bloomed yet or had already bloomed.
Similar with the Viola, some of the flowers are drawn all blue, which is more like other types that do not have leaves like the ones drawn.