Camera Lucida
Many of the microscopic features that were illustrated were
done so using the camera lucida technique, where an image of the object being viewed on a microscope's stage is superimposed onto
the drawing surface. This is especially important in guaranteeing the accuracy of the scaling of the structures illustrated, some of which
are only one to a few millimeters long or wide. 
John Hayden, at the University of Richmond, allowed for the use of his lab, microscope, and camera lucida for many of the Flora of Virginia illustrations, including most on this site.