THE JOURNAL OF PHARMACOLOGY. 



163 



exception of a single layer of cells ad- 

 jacent to the phloem groups which 

 are noticeably larger than the others 

 and of a uniform rectangular shape. 



The phloem groups within are com- 

 posed of thick-walled bast fibers of a 

 brownish - yellow color and angular 

 outline. They are very compact, form- 

 ing a firm casing for a stem which 

 is otherwise rather weak. The sieve- 

 tubes, seen more distinctly in the longi- 

 tudinal section, Fig. 3, are few. They 

 are of the usual type, and are much 

 larger than the bast fibers. The inner 

 portions of the phloem groups grad- 

 ually merge into the cambium layer, 

 which is about three cells in width and 

 of the usual oblong thin-walled type. 



The xylem, or woody portion of the 

 fibro-vaseular bundle next within the 

 cambium layer, is composed of rather 

 thick-walled tracheids, rectangular in 

 outline with small intercellular spaces, 

 and becoming more irregular toward 

 the center. Interspersed among these 

 are the larger ducts, fewer near the 

 cambium but becoming more numerous 

 toward the center. They are arranged 

 in radial rows of from four to eight, 

 decreasing in size toward the center. 



The medullary rays are very indis- 

 tinct, being marked merety by the 

 slight radial elongation of their cells.- 



The central parenchyma is composed of the usual large, round, thin- 

 walled cells, with large intercellular spaces. 



The longitudinal section shown in Fig. 3 is perhaps of more importance 

 than the cross-section, since it shows the parts of the stem as they would 

 appear in a powder of the drug. The cells of the epidermis are much 

 elongated, those of the outer parenchyma but slightly so. The bast-fibers 

 within are in a compact, confused mass, their lumens being distinguishable 

 only with difficulty. The cambium layer, owing to its delicacy, is difficult 

 to preserve in a perfect condition. The usual brick-shaped central cells 

 merge into the bast fibers on the outer side and into the ducts and tracheids 

 on the inner side. 



Fig. 2. 



