388 



SCIENTIFIC AND APPLIED PHARMACOGNOSY 



of wood, and forming the keel on drying; odor slight, penetrating; 

 taste sweetish and acrid. 



Inner Structure. An outer layer of several rows of tangentially 

 elongated, light yellowish or yellowish-brown cells; outer bark of 

 slightly thickened cells, containing a colorless or pale yellowish 

 amorphous substance, which is liberated in the form of large glob- 

 ules upon the addition of a solution of potassium hydroxide; inner 

 bark, the cells in radial rows, consisting of parenchyma, small groups 

 of leptome, and medullary rays, the latter 1 to 3 cells wide all the 

 cells in this zone show a collenchymatous thickening of the walls 

 and contain an amorphous substance, similar to that found in cells 

 of the outer bark; woody layer of tracheae with bordered pores, wood 

 fibers with oblique, simple pores, tracheids, and medullary rays, the 



FIG. 169. Transverse sections of senega, the two on the left being of the dry 

 drug, and the one on the right showing the appearance after soaking 

 the material in water: R, outer bark; R', bark on the side having abnormal 

 development of wood; B, inner bark, which gives rise to the "keel " on the 

 drying of the root; H, wood; C, C', cambium; m, medullary rays; m', 

 parenchyma developed in place of wood on one side. After Meyer. 



latter being rather indistinct and resembling the wood fibers; tissues 

 of the central layer of wood colored yellowish- or reddish-brown 

 on the addition of a solution of potassium hydroxide. 



Powder. Light yellowish-brown or dark yellow; odor penetrat- 

 ing; slightly sternutatory; sclerenchymatous fibers thick-walled, 

 non-lignified, with oblique simple pores; tracheae about 0.175 mm. in 

 length, lignified, with simple and bordered pores; medullary-ray 

 cells somewhat lignified, with large simple pores. Quillaja (Fig. 136) 

 is distinguished from senega by having elongated monoclinic prisms 

 of calcium oxalate, and numerous starch grains, lignified bast fibers 

 and stone cells. 



The following test is of some practical use in arriving at a compar- 

 ative value of different samples of senega. It is based upon the 

 presence of methyl salicylate, which occurs in greatest amount in 



