RHIZOMES AND ROOTS. 



257 



PLATE CXIII. 



FIG. 123. Powdered Rhubarb Rhizome ( x 240). 



a, Starch grains. 



ca, Cambium cells. 



cr, Crystals of calcium oxalate. 



I, Bast. 



m, Pith. 



pc, Cortical parenchyma. 



pi, Parenchyma of wood. 



rm, r'm', Medullary rays in transverse and tangential section. 



v, Vessels. 



vg, Obliterated sieve tubes; 



