(The upper part of the figure represents a vertical section of the tube.)
This image is from _ in Pereira's Elements of Materia Medica and Therapeutics, 1854.
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.
http://www.henriettes-herb.com - Copyright 1995–2022 Henriette Kress.