Here are some more plant fossils from the Florissant formation that I found 20 years ago.
This is only a partial leaf but it reminds me of an alder tree
Some sort of evergreen foliage I think.
Both halves of a partial oak leaf
The Florissant formation is the remains of a temporary lake that is dated to the Eocene period (Priabonian stage) and is located in Colorado.
If you want a good book with pictures of some spectacular fossils that have been found in the Florissant formation, check this book out: Fossils of Florissant, by Herbert W Meyer.