Vegetable Materia Medica of the U.S. or Medical Botany, 1818 (2nd ed. 1825), was written by William P. C. Barton, M. D.
Henriette's herbal is one of the oldest and largest herbal medicine sites on the net. It's been online since 1995, and is run by Henriette Kress, a herbalist in Helsinki, Finland.
Plant Healer Magazine: Very relevant to the practitioner.
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