98 PLANT ORGANS OR PARTS OF PLANTS. 



Description. — The root is cylindrical, somewhat taper- 

 ing, I to 2 cm. thick, grayish-brown externally, deeply 

 furrowed longitudinally, and somewhat transversely 

 above. Fractures smoothly, with discharge of dust; 

 internal surface, white or yellowish-brown. Taste first 

 sweetish, then bitter and acrid. 



Histology. — With the lupe a dirty white, mealy cortex 

 is found within the grayish-brown periderm. It is 

 separated from the wood by the cambium, and does not 

 show a radial arrangement. The woody portion of the 

 main root is radially striated at its periphery ; in the 

 branches this stria tion is very fine, and is continued to the 

 centre with interruptions. In the centre itself a large 

 vascular strand is found. Higher powers disclose several 

 layers of brown cork cells in the periderm. The cortex 

 consists of parenchyma cells, with a tangential elongation 

 in the outer part of the section, but more rounded or 

 quadrate internally. They are filled with starch and 

 calcium oxalate crystals. The central portion is made 

 up of alternating xylem bundles and medullary rays, not 

 extending to the centre. The former are broad, and con- 

 sist of a ground-work of thin-walled cells in which radially 

 arranged groups of vessels are imbedded. The medullary 

 rays consist of amylaceous parenchymatous cells, which 

 become continuous with the central parenchyma. The 

 centre of the section shows a firm bundle of vessels. 



Powder. — The powder of belladonna is usually grayish- 

 brown in color. 



The main histological elements found are starch, 

 tracheids, fibres, and cork. Crystal sand forms an incon- 

 spicuous element of the powder. 



The starch grains are numerous ; they are both simple 

 and compound, the compound varieties perhaps about as 

 many as the simple forms. The compound granules exist 

 in twos, threes, occasionally in fours. The average diam- 

 eter of the simple grains is about 18 microns; individual 



