(14 diam.) A, Cork. B, Parenchyma of cortex. C, Vascular bundle. D, Medulla. (Photomicrograph).
This image is from Aconitum in Sayre's Manual of Organic Materia Medica and Pharmacognosy, 1917.
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.
http://www.henriettes-herb.com - Copyright 1995–2016 Henriette Kress.