Time for another comparison. The larger leaf on the left is the common species of Papala kepau (Pisona umbellifera) in the Ko’olaus. The one on the right is the rarer Pisona sandwicensis. As you can see, the leaf bases are much different. P. sandwicensis has a much more truncate leaf base and a better defined petiole, whereas P. umbellifera has a cuneate base and less of a petiole. Naturally, there are other differences as well. But I hope this helps in the field.