The hairs of the base of the ligulate petals of calendula (Plate 10, Fig. 2) are biseriate. The hairs are very long and the walls are very thin.
=Multicellular uniseriate branched hairs= occur on the leaves of dittany of Crete, mullen, and on the calyx of lavender flowers.
The dittany of Crete (Plate 11, Fig. 3) hair is smooth-walled, and the branches are alternate.
In mullen (Plate 11, Fig. 1) the hairs have whorled branches, the walls are smooth, and the cell cavity usually contains air.
MULTICELLULAR MULTISERIATE NON-BRANCHED HAIRS
1. Cumin (_Cuminum cyminum_, L.). 2. Marigold (_Calendula officinalis_, L.).]
1. Mullen leaf (_Verbascum thapsus_, L.). 2. Lavender flowers (_Lavandula vera_, D. C.). 3. Dittany of Crete (_Origanum dictamnus_, L.).]
The lavender hairs (Plate 11, Fig. 2) have mostly opposite branches, and the walls are rough. Thus the multicellular branched hairs may be divided into subgroups which have alternate, opposite, whorled, or in certain hairs irregularly arranged branches. Each class may be again subdivided according to color, character of cell termination, etc., as cited at the beginning of the chapter.
Occasionally multicellular hairs assume the form of a shield (Plate 12, Fig. 1); in such cases the hair is termed peltate, as in the non-glandular multicellular hair of shepherdia canadensis.
Hairs grow out from the surface of the epidermis in a perpendicular, a parallel, or in an oblique direction. Hairs which grow parallel or oblique to the surface are usually curved, and the outer curved part of the wall is usually thicker than the inner curved wall.
The mature hairs of some plants consist of dead cells. In other plants the cells forming the hair are living. When dried, those hairs, which were dead before drying, contain air; while those hairs which were living before drying, show great variation in color and in the nature of the cell contents. The contents are either organic or inorganic. The commonest organic constituent is dried protoplasm. In cannabis indica are deposits of calcium carbonate.
=Multicellular multiseriate branched hairs= are the ultimate division of the pappus of erigeron, aromatic goldenrod, arnica, grindelia, boneset, and life-everlasting.