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 oresent, 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, 



