Fig. 207. Gentiana lutea - Cross-section.
A, Cork. B, Parenchyma of cortex. C, Water tubes. D, Parenchyma of xylem.
This image is from Gentiana in Sayre's Manual of Organic Materia Medica and Pharmacognosy, 1917.
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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.