In 1919, the American biologist John Ernest Weaver published The Ecological Relations of Roots, a study of the root-systems of desert plants. It contains some truly amazing hand-drawn illustrations of roots; he credits Annie Mogensen and F. C. Jean for working on the images.
I'd love to blow up one of these as a huge poster to put on my wall! I'm not sure if I could get scans high-res enough to make them really big, but the whole book is scanned and in the public domain over the Internet Archive.
I originally found these via a post about Weaver's book over at Socks, where the bloggers clipped out some of the most striking images; but below are a few of my faves …
