POWDERED DRUGS AND FOODS. 



733 



48. JALAPA. — Dark yellow ; crystals of calcium oxalate in 

 rosette aggregates, 30 to 35 /jl in diameter ; starch grains ellipsoidal 

 and ovoid, with somewhat excentral lamellae, 15 to 35 ./a in diam- 

 eter, I- to 3-compound and in some cases more or less swollen; 

 resin cells yellowish-brown; sclerenchymatous fibers few, with 

 simple pores (Fig. 195). Tubers deficient in resin are lighter in 

 color, contain more starch and less calcium oxalate. 



Pig. 289. Rhubarb: C, rosette aggregates of calcium oxalate; P, parenchyma 

 containing starch grains (S) ; T, tracheae; E, sieve; R, reddish-brown masses. 



49. RHEUM. — Yellowish-brown (Figs. 281, A; 289) ; crys- 

 tals of calcium oxalate in rosette aggregates, 50 to 100 /* in diam- 

 eter; starch grains somewhat spherical, 5 to 20 /i in diameter, 

 either single or 2- to 4-compound ; tracheae few, scalariform. The 

 powder is colored reddish with alkalies. A common adulterant 

 is " wheat middlings." (See No. 239.) The exhausted drug 

 is frequently added to the powder and may be detected by the 

 somewhat altered starch grains and the decrease in the amount 

 of the aqueous or dilute alcoholic extract, which in genuine 

 rhubarb is about 35 per cent. 



