A question about a recipe: Peach-Plum-Lime-Ginger Jam

I have a question about step 3 on the recipe "Peach-Plum-Lime-Ginger Jam" from em-i-lis. It says:

"In a large stockpot, put the plums, peaches, lime zest and juice, crystallized ginger, allspice, 1/2 c sugar, water and cider. Bring to a boil and cook, stirring regularly, 10-15 minutes."

Probably dumb question, but you don't peel the Italian plums?