I’ve been trying to find out what species the legendary moss-leaved dandelion (as featured in my book) and some other cultivated varieties actually are. I took the series of detailed pictures below of this plant last spring and posted them on the Dandelions of Britain and Ireland group (there are several experts of Taraxacum there including author of the Field Handbook to British and Irish Dandelions, John Richards)
Dutch expert Karst Meijer has ID’d the plant as Taraxacum tortilobum. We cannot be 100% sure that this is the original plant depicted in the Vegetable Garden (1920), but it makes sense that it was a wild plant that was domesticated as dandelion breeding is difficult as they are largely apomictic. T. tortilobum is found in the wild in northern France, which strengthens the theory that this is the plant. See https://www.gbif.org/species/5394131 where it is known as the twisted-lobed Dandelion.
The plant I grow which is the only line claiming to be the moss-leaved dandelion originated from IPK Gatersleben (German genebank) as Taraxacum sublacionosum “Delikatess” which it isn’t!