Learn English – word for the opposite of being hollow

I'm looking for an adjective that describes an object that, rather than is just the outside, is instead just the inside.

Searching for antonyms of hollow, I have only found the word solid, which suggests both the inside and outside of an object.

I really need a way to describe something as being just the inside of something.

I can only think of words like core or heart to describe what I'm looking for, but those are nouns.

When a tree has only its exterior, the tree is hollow. It is a hollow tree.

When a tree has only its interior, the tree is _____. It is a _____ tree.

Perhaps tree was a bad example, it was the only object I could think of at the time that made sense to be a hollow object. Any object where that description could apply is a reasonable substitute, it does not have to be specifically about a tree.