1. Epidermis of leaf showing the wavy epidermal cells, stoma, and a clustered hair. 2. Surface view of the petal epidermis. 3. Non-glandular hair from the calyx or corolla. 4. Long, thin-walled, twisted, non-glandular hairs from the leaves and stem. 5. Unicellular non-glandular hair from the tube of the corolla. 6. Glandular hairs with a one-celled stalk and with two secreting cells divided by vertical walls. 7. Surface and side view of the eight-celled glandular hairs. 8. Conducting cells. 9. Fibres from the stem. 10. Pollen grains.] [Illustration: PLATE 98 SPURIOUS HOREHOUND (_Marrubium peregrinum_, L.) 1. Surface view of the leaf epidermis. 2. View of the petal epidermis. 3. Non-glandular multicellular branched hair from the stem, leaves, or flowers with a few of the lower branches broken. 4. Broken pieces and branches from the compound hairs scattered throughout the field. 5. Unicellular glandular hair with a two-celled stalk. 6. Under-surface view of an eight-celled glandular hair. 7. Side view of eight-celled glandular hair. 8. Long, pointed, unicellular, non-glandular hair from the corolla, the wall irregularly thickened near the apex. 9. Fibres. 10. Pollen grains, 11. Conducting cells of leaf.] [Illustration: PLATE 99 POWDERED INSECT FLOWER STEMS (_Chrysanthemum cinerariifolium_, [Trev.], Vis.) 1. Surface view of epidermis. 2. Cross-section of epidermis. 3. Hairs. 4. Fibres. 5. Cross-section of fibres. 6. Longitudinal view of pith parenchyma. 7. Cross-section of pith parenchyma. 8. Conducting cells.] The wavy leaf epidermis (1) with stoma; the beaded wall petal epidermis (2); the non-glandular, multicellular branched hairs (3) from the stem leaves or flowers; the broken pieces and branches of the compound hairs (4) scattered throughout the field; the glandular hairs (5) with a two-celled stalk; the eight-celled glandular hair (7) seen in surface view and a side view (8) of a similar hair; the long, pointed, unicellular non-glandular hair from the tube of the corolla, the wall irregularly thickened near the apex; the fibres (9) from the stem; the pollen grains (10) with prominent centrifugal projections; the conducting cells. The diagnostic elements of marrubium peregrinum are the multicellular branched hairs (3) which occur on all parts of the plant, usually much broken in the powder, with walls many times thicker than the walls of the hairs found in U. S. P. horehound; the pollen grains (10) with centrifugal projections and the stalked glandular hairs (5). INSECT FLOWER STEMS