Answer:
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair
Old Mcdonald had this
This is a dish containing beans, sometimes baked but, despite the name, usually stewed, in a sauce
What cleans as it gets dirty only to get clean the more you use it?
Take it and you will lose or gain more than all the others.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.