STEMS 



241 



field; the glandular hairs (5) with a two-celled stalk; the eight- 

 celled glandular hair (7) seen in surface view and a side view (8) 

 of a similar hair; the long, pointed, unicellular non-glandular 

 hair from the tube of the corolla, the wall irregularly thickened 

 near the apex; the fibres (9) from the stem; the pollen grains 

 (10) with prominent centrifugal projections; the conducting 

 cells. 



The diagnostic elements of marrubium perigrinum are the 

 multicellular branched hairs (3) which occur on all parts of the 

 plant, usually much broken in the powder, with walls many 

 times thicker than the walls of the hairs found in U. S. P. hore- 

 hound; the pollen grains (10) with centrifugal projections and 

 the stalked glandular hairs (5). 



INSECT FLOWER STEMS 



Insect flower stems are the chief adulterant of insect flowers. 

 Until the passage of the insecticide law, it was a common practice 

 to sell (for insect powder) a mixture of powdered stems and 

 flowers. Since the passage of the law, the presence of the stems 

 in a powder is supposed to be declared on the label. In spite 

 of the penalties attached, their presence in a powder is frequently 

 not declared, as evidenced by a microscopical examination of 

 the insect powders obtained in the open market. 



The structure of powdered insect flower stems (Chart 99) is 

 as follows: 



The epidermal cells of the stems are prominently marked 

 with stoma and angled, striated wall cells (Fig. 1). On cross- 

 section (Fig. 2) the stem is seen to be made up of epidermal 

 cells with thick outer and thin side walls (Fig. 2) . The T-shaped 

 hairs (Fig. 3) are longer than those found on any other part of 

 the plant. The fibres (Fig. 4) are the most characteristic part 

 of the powder. They are elongated, and the walls are white 

 and slightly porous and of nearly uniform thickness. They 

 occur free in the field or in groups of two or more. The 

 cross-section view of these fibres is shown in Fig. 5. The pith 

 parenchyma (Fig. 6) is abundant and is composed of thick, 

 porous- walled cells. On cross-section the cells are rounded 

 and are separated by intercellular spaces. The conducting cells 

 (Fig. 8) vary from spiral to reticulate. 



