VEGETABLE POWDERS 



185 



...... 



Scale in Microns 



Fig. 3. ACHILLEA. 



a. Upper and lower epidermis. 



b. Epidermis of petiole and stems. 



c. Pollen grains. 



d. Trichomes. 



. Bast of vascular bundles. 



/, g. Tracheids and ducts of vascular bundles. 



h. Prismatic crystal bearing fibers. 



i. Side view of epidermal tissues. 



j. Prismatic crystals and starch. 



