Apocynum cannabinum. Apocynum androsaemifolium.
Bast cells. Transverse sections.
This image is from The Roots of Apocynum Androsaemifolium and Apoc. Cannabinum. in the November issue of the AJP 1881.
A herbal distance course
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.