PLATE 60
Glandular Hairs
1. Kamala (Mallotus philippinensis, [Lam.] [Muell.] Arg.).
2. Digitalis leaf (Digitalis purpurea, L.).
3. Peppermint leaf (Mentha piperita, L.).
4. Lupulin.
5. Cannabis indica leaf (Cannabis saliva, L.).
Multicellular multiseriate stalked glandular hairs occur on the stems and leaves of cannabis indica (Plate 60, Fig. 5).
In the glandular hair of kamala (Plate 60, Fig. 1) the number of secretion cells is variable and papillate in form, and the cuticle is separated from the secretion cells.
In the glandular hair of hops the outer wall or cuticle is torn away from the secretion cells, and the cavity thus formed serves as a storage cavity. This distended cuticle of the hops shows the outline of the cells from which it was separated.
In the glandular hairs of the mints the secreted products (volatile oils) are stored between the secretion cells and the outer detached cuticle. This cuticle is elastic, and it becomes greatly distended as the volatile oil increases in amount.
In many of the so-called glandular hairs, tobacco, belladonna geranium, etc., the synthetic products are retained in the glandular cells, there being no special cavity for their storage.
These hairs usually contain an abundance of chlorophyll.
The division wall of multicellular glandular hairs may be vertical, as in the two-celled hair of digitalis (Plate 60, Fig. 2); as in horehound (Plate 97, Fig. 6), and as in peppermint (Plate 60, Fig. 3); in this case there are eight cells, and they form a more or less flat plate of cells.