Here is one I took earlier today. This is a non commercial potato called Papa chonca. This is the first year I have grown it and this is the first of the 3 plants I have that I am harvesting. The others will wait until after a frost. I am told it is a near perennial due to the huge numbers of tubers (mostly small).
If you look at this picture, the top yellow line was the soil level at harvest. The middle yellow line is the height of the buried stem that has tubers growing on the stem. There are two mini tubers growing within the rectangle. Not on roots, not on stolons off the roots. The bottom yellow line is the original soil height before hilling. The middle rectangle also show another slightly further down the stem, but it is harder to see. The bottom rectangle shows minitubers growing on stolons that were below soil level.
I have not weighed the yield, but there were at least 45 tubers large enough to eat. I reburied anything smaller than a half inch to see if they come up again in the spring.
Here is a closeup of the tubers forming on the stem.
Here is a medium range shot
And one last one showing about half the yield. I hadn't dug out half the plant but I forgot to take another one after I dug the rest of it out.
I also dug 7 Purple Peruvian fingerling plants today. I'll post this picture as well even though it isn't very clear, but there are tubers growing along the stolons on this one too.
And here's one I pulled off Facebook someone posted the other day of YEMA DE HUEVO. You can see the tubers forming and bulking up the length of the stolons. This makes total sense when you think about the fact that potato tubers are not really tubers at all, but are merely modified stems.
