=Branched solitary unicellular hairs= occur on the leaves of hesperis matronalis (Plate 7, Fig. 8), and on galphimia glauca (Plate 7, Fig. 9). The hair of hesperis matronalis has smooth walls, and the two branches grow out nearly parallel to the leaf surface. The hair of galphimia glauca has rough walls, and the two branches grow upward in a bifurcating manner. MULTICELLULAR HAIRS =Multicellular= hairs are divided into the uniseriate and the multiseriate hairs. Both of these groups are divided into the branched and the non-branched hairs, as follows: 1. =Uniseriate=. (_A_) =Non-branched.= (_B_) =Branched.= 2. =Multiseriate.= (_A_) =Non-branched.= (_B_) =Branched.= =Multicellular uniseriate non-branched hairs= occur on the leaves of digitalis, Western and Eastern skullcap, peppermint, thyme, yarrow, arnica flowers, and sumac fruit. [Illustration: PLATE 9 MULTICELLULAR UNISERIATE NON-BRANCHED HAIRS 1. Digitalis leaf (_Digitalis purpurea_, L.). 2. Arnica flower (_Arnica montana_, L.). 3. Western skullcap plant (_Scutellaria canescens_, Nutt.). 4. Eastern skullcap plant (_Scutellaria lateriflora_, L.). 5. Peppermint leaf (_Mentha piperita_, L.). 6. Thyme leaf (_Thymus vulgaris_, L.). 7. Yarrow flowers (_Achillea millefolium_, L.). 8. Wormwood leaf (_Artemisia absinthium_, L.). 9. Sumac fruit (_Rhus glabra_, L.).] Digitalis hairs (Plate 9, Fig. 1) are made up of a varying number of uniseriate-arranged cells of unequal length, frequently placed at right angles to the cells above and below; the walls are of a whitish color, and are rough or smooth. Eastern skullcap (Plate 9, Fig. 4) has hairs with not more than four cells; these hairs are curved, and the walls are whitish, sometimes smooth, but usually rough. In Western skullcap (Plate 9, Fig. 3) the hairs have sometimes as many as seven cells. The walls are white and rough, and the individual cells of the hair are much larger than are the cells of the hairs of true skullcap. Peppermint (Plate 9, Fig. 5) has from one to eight cells. The hair is curved, and the walls are very rough. Thyme (Plate 9, Fig. 6) has short, thick, rough-walled trichomes, the terminal cell usually being bent at nearly right angles to the other cells. Yarrow hairs (Plate 9, Fig. 7) have a variable number of cells. In all the hairs the basal cells are short and broad, while the terminal cell is greatly elongated. Arnica hairs (one form, Plate 9, Fig. 2) have frequently as many as four cells, the terminal cell being longer than the basal cells. The walls are white and smooth. Sumac-fruit hairs (Plate 9, Fig. 9) have spindle-shaped, reddish-colored hairs. =Multicellular multiseriate non-branched hairs= occur on cumin fruit and on the tubular part of the corolla of calendula.