Matisse: Still Life with Shellfish

I see what looks like a stem on the right end of it. I think it was originally more greenish, and might be a sort of melon.

I believe you are right. He painted several artworks called Still Life with Shellfish, I found a melon in another painting.

I hadn't noticed that. Thank you for pointing it out! I was under the impression that it was a sack, and now I think that it is a drawstring bag. The thing which you are calling a stem looks to me like a cord with a knot in it.