520 



SCIENTIFIC AND APPLIED PHARMACOGNOSY 



Ca 



FIG. 218. Transverse section of gelsemium near the cambium: P, parenchyma; 

 S, sieve; C, cambium; Ca, calcium oxalate crystals; SK, SF, wood fibers; 

 T, tracheae; MR, medullary rays. 



FIG. 219. Gelsemium: A, longitudinal section of the rhizome showing the 

 separation of acicular crystals of the nitrates of the several alkaloids. The 

 sections are allowed to remain in a desiccator, exposed to the vapors of nitric 

 acid, for about 12 hours. They are then mounted in paraffin oil, and 

 allowed to stand for several hours, when the alkaloids should separate in 

 the form of small needles throughout the parenchyma tissue. Some of the 

 crystals form feather-shaped aggregates at or near the edges of the section, 

 as shown to the right in the illustration. In the figure above are shown, also, 

 the long prismatic crystals of calcium oxalate in the cells of the medullary 

 rays, which are unaffected by the vapors of the acid. After Tunmann. 

 Pflanzenmikrochemie. 



