74 HISTOLOGY OF MEDICINAL PLANTS 



number of uniseriate-arranged cells of unequal length, frequently 

 placed at right angles to the cells above and- below; the walls 

 are of a whitish color, and are rough or smooth. 



Eastern skullcap (Plate 9, Fig. 4) has hairs with not more 

 than four cells; these hairs are curved, and the walls are whitish, 

 sometimes smooth, but usually rough. In Western skullcap 

 (Plate 9, Fig. 3) the hairs have sometimes as many as seven 

 cells. The walls are white and rough, and the individual cells 

 of the hair are much larger than are the cells of the hairs of 

 true skullcap. 



Peppermint (Plate 9, Fig. 5) has from one to eight cells. 

 The hair is curved, and the walls are very rough. 



Thyme (Plate 9, Fig. 6) has short, thick, rough- walled 

 trichomes, the terminal ceU usually being bent at nearly right 

 angles to the other cells. 



Yarrow hairs (Plate 9, Fig. 7) have a variable number of 

 cells. In all the hairs the basal cells are short and broad, while 

 the terminal cell is greatly elongated. 



Arnica hairs (one form, Plate 9, Fig. 2) have frequently as 

 many as four cells, the terminal cell being longer than the basal 

 cells. The walls are white and smooth. 



Sumac-fruit hairs (Plate 9, Fig. 9) have spindle-shaped, 

 reddish-colored hairs. 



Multicellular multiseriate non-branched hairs occur on 

 cumin fruit and on the tubular part of the corolla of calendula. 



The hairs on cumin fruit \'ary considerably in size. All the 

 hairs are spreading at the base and blunt or rounded at the apex. 

 The cells forming the hair are narrow and the walls are thick. 

 Three differently sized hairs are shown in Plate 10, Fig. i. 



The hairs of the base of the ligulate petals of calendula 

 (Plate ID, 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. i) the hairs have whorled branches, 

 the walls are smooth, and the cell cavity usually contains air. 



The lavender hairs (Plate 1 1 , Fig. 2) have mostly opposite 



