The site below defines the following:
Butternut - This endangered hardwood (also called the "White Walnut") is
being threatened by a dangerous fungus.
American Sycamore - Sometimes referred to as a "Butterwood", the American
Sycamore tree can live 500 years or longer.
There are many other trees listed at this site and all with links for more
info. The following intro is given:
Welcome to the Molecular Expressions Tree Collection featuring
photomicrographs (photographs taken through a microscope) of thin sections of
wood from various trees. Each entry contains a cross, radial, and transverse
section of wood accompanied by an abstract of information about the
I had hoped this would help but there seems to be more than one answer
judging by the responses.