RADIX RHEI. RHUBARB. II3 



If only part of the centre is removed, fine, white striae 

 appear upon the surface, which alternate regularly mth 

 yellowish-red lines. Where the cortex is removed en- 

 tirely, the tortuous groups of vascular channels will form 

 a rhombic network. If the woody ring is cut away, 

 the medullary portion will come to view with a number of 

 scattered, circularly arranged rays upon the surface. 

 The granular fracture line shows a meshwork of reddish- 

 browTi lines and ' dark dots upon a white ground sub- 

 stance; a regular arrangement is noticed only with the 

 cylindrical, lateral branches. Here a yellowish-brown 

 cambium line runs parallel and close to the outer circum- 

 ference; tortuous medullary rays radiate through the 

 parts external to this, to end in a light zone internal to the 

 cambium. The medulla is colored irregularly red and 

 brown and also shows still darker rays without any 

 typical distribution. The whole surface is mottled. 



Under the microscope, the white ground-substance 

 consists of thin-walled parenchymatous cells containing 

 starch and calcium oxalate. Every mottling which 

 reaches a diameter of i cm. is made up of ten to twenty 

 narrow, dark-brown medullary rays, which run from a 

 central point. The dark line which divides every mot- 

 tling into two halves consists of cambium tissue. Internal 

 to this cambium, small-celled parenchyma containing 

 starch and calcium oxalate is found between the brown 

 medullary rays; externally tracheids and ring-shaped 

 vascular channels abound. The medullary rays con- 

 sist of two or three layers of radially elongated cells which 

 are filled with yellowish -brown masses. The red and 

 white mottling of the medulla is due to the presence of 

 these masses or starch. 



Powder. — This is reddish to yellow-brown, is gritty 

 between the teeth, and when mixed with water or saliva 

 it imparts to it an orange-red tinge. Microscopically the 

 following elements are usual: Crystals, starch, peculiar 



