a. Cuticle or epidermis.
b. Outer cortical layers.
c. Red inner cortical layers.
d. Cellular sheath.
e. Woody zone.
f. Medulla or pith.
This image is from Sarsaparilla 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.