164 HISTOLOGY OF MEDICINAL PLANTS 
the chlorophyll, and by adding Lugol’s solution. If starch is 
present, the contents of the cells will become bluish black; but 
if no starch is present, the cells remain colorless. 
GLANDULAR TISSUE 
The glandular tissue of the plant is divided into two groups, 
according to where it occurs. These groups are, first, external 
glandular tissue, and secondly, internal glandular tissue. The 
most important external glandular tissue is composed of the 
glandular hairs. These are divided into two groups: first, 
unicellular; and secondly, multicellular glandular hairs. 
UNICELLULAR GLANDULAR HAIRS 
The unicellular glandular hairs are either sessile or stalked. 
Sessile unicellular hairs occur in digitalis leaves. 
Stalked unicellular hairs of digitalis are shown on Plate 60, 
Fig. 2. 
Unicellular uniseriate stalked glandular hairs occur on the 
stems of the common house geranium (Plate 61, Fig. 2), on the 
leaves of butternut, the leaves and stems of marrubium peregri- 
num (Plate 98, Fig. 5), and in arnica flowers. The stalk varies 
from two to ten cells; in eriodictyon the cells vary from four 
to eight cells. 
Unicellular multiseriate stalked glandular hairs are not of 
common occurrence. 
MULTICELLULAR GLANDULAR HAIRS 
Multicellular glandular hairs are divided into two groups: 
first, sessile; and secondly, stalked hairs. 
Multicellular sessile glandular hairs occur on the leaves of 
peppermint (Plate 60, Fig. 3), horehound (Plate 97, Fig. 7), 
and in hops (Plate 60, Fig. 4). In each of these hairs there are 
eight secretion cells. 
Stalked glandular hairs are divided into two groups: first, 
uniseriate stalked; and secondly, multiseriate stalked glandular 
hairs. 
Multicellular uniseriate stalked glandular hairs occur on 
the leaves of tobacco (Plate 61, Fig. 4), belladonna (Plate 61, 
