A common adulterant found in open insect flowers is the flower-heads of European daisy (_C. leucanthemum_). Examination of powdered flowers exported from Europe shows that the entire flower-head is ground and mixed with the insect flowers. In the cheaper varieties of open flowers, only the tubular flowers are added after they have been separated from the heads by crushing and sifting. These tubular flowers so closely resemble the tubular flowers of the true insect flowers that it is practically impossible to distinguish between them macroscopically. The quickest and surest way to identify them is to reduce a portion of the flowers to a fine powder and examine it microscopically. Certain structures of the white daisies (Plate 120) are somewhat similar to those found in insect flowers. These structures are the papillæ of the ray petal (Figs. 3, 5, and 13), the lobe of the disk petal (Fig. 14), and the lobe of the stamen and the pollen (Fig. 8). The differences are as follows: The under epidermis of the ray flowers is composed of wavy cells which are more elongated than the ray flowers of the under epidermis of the ray petal of insect flower. The filament tissue is made up of slightly beaded cells instead of smooth-walled cells. The papillæ of the stigma are smaller than the papillæ of insect flowers. The most striking difference is found in the structure of the achene. The epidermal tissue of the achene is composed of palisade cells (Fig. 10), which in the mature form have thick white walls and scarcely any cavity. These cells swell perceptibly when placed in water. The other striking feature of the achene is the bright red resin masses which occur free in the field. Even a small trace of daisies in insect powder can be identified. [Illustration: PLATE 120 POWDERED WHITE DAISIES (_Chrysanthemum leucanthemum_, L.) 1 and 2. Scale tissue. 3, 5 and 13. Papillæ of petals. 4. Scale tissue. 6. Lobe of ray petal. 7. Filament tissue. 8. Pollen. 9. Papillæ of stigma. 10. Palisade cells of achene. 11. Resin masses. 12. Parenchyma of receptacle. 14. Lobe of dish petal.] When studying flowers there should be considered the number and structure of pollen grains; the nature of the papillæ of the stigma and the petals; the nature of the hairs of the corolla and calyx, when present. In the composite flowers we should also consider the structure of the involucre scales, and, when present, the structure of the receptacle scales, as in the case of anthemus, and of the pappus hairs, as in the flowers of arnica, boneset, grindelia, and aromatic goldenrod. CHAPTER VIII FRUITS