Here is a cool Flickr find. Jordyn Meredith , an art student in Baltimore, has licensed her digital dendrology collection under a CC Attribution, Share-Alike license. These are absolutely gorgeous digital microscope shots of tree cross-sections. My favorite is Lilac Chastetree.
From her description:
“After identifying the type of tree to which the branch belongs, I use a digital camera attachment on my microscope to photograph the samples. Piecing together over fifty photographs for each sample, each final image is a 100x magnification of a glimpse of life not seen by the human eye alone. They become abstract structures reminiscent of any number of things.”