POWDERED DRUGS AND FOODS. 



775 



The powder is frequently admixed with tonka, which is easily 

 determined by the presence of starch grains (see No. 144). Some 

 of the so-called vanilla powders are mixtures containing vanillin 

 or coumarin but none of the tissues of either vanilla or tonka. 



Fig. 312. Cloves: B, bast fibers; A, fragments of anther showing cells with char- 

 acteristic marking or thickening of the walls; P, pollen grains which appear triangular in 

 outline when mounted in water: O, oil glands, the large one to the left being from a petal; 

 E, surface view of epidermal cells of petal; P, parenchyma; C, calcium oxalate; T, tracheae; 

 St, seven stone cells from the young branches or twigs, the so-called "clove stems." 



2. Seeds Wanting. 



179. VIBURNUM OPULUS. Light brown ; calcium oxal- 

 ate in monoclinic prisms, or few rosette aggregates 15 to 30 ^u 

 in diameter ; crystal fibers with monoclinic prisms of calcium 

 oxalate ; stone cells few, relatively thick-walled ; bast fibers numer- 

 ous, lignified. 



