POWDERED DRUGS AND FOODS. 791 



fragments of palisade cells and the somewhat elongated, narrow, 

 sclerenchymatic fibers which cross one another. 



240. RYE FLOUR is faintly grayish-white, the starch grains 

 closely resembling those of wheat, but sometimes larger (20 to 

 60 fx) ; the lamellae are distinct and the point of origin of growth 

 is sometimes marked by a star-shaped cleft or fissure. Rye 

 flour when mixed with water does not agglutinate like wheat flour. 

 A few fragments of the pericarp are also present (Fig. 321). 



241. RYE MIDDLINGS. In addition to the starch grains 

 in rye flour a considerable amount of the tissues of the pericarp 

 are present. The latter closely resemble those of wheat, but hairs 

 from the apex of the fruit have thinner walls, the lumen being 

 2 or 3 times the thickness of the walls ; and the tangentially 

 elongated cells have simple pores only on the tangential walls, 

 and do not lie close together, so that there are intercellular 

 spaces between them (Fig. 321). 



242. BARLEY FLOUR. The starch grains closely resemble 

 those of wheat, but are smaller, usually not more than 25 /x in 

 diameter, and in the case of malt the grains show distinct radial 

 and circular clefts, due to the action of the diastase ; the hairs 

 from the apex of the grain resemble those of both wheat and 

 rye but are shorter than either, being from 40 to 150 ;u, long; 

 the tangentially elongated cells are non-porous, the walls being 

 I to 2 /x thick (Fig. 321). 



243. BUCKWHEAT FLOUR. Light grayish-brown ; peri- 

 carp of elongated epidermal cells with latticed walls, due to the 

 pores of the outer and inner walls running obliquely and at right 

 angles to each other; short sclerenchymatic fibers with somewhat 

 curved or oblique end walls, large simple "pores and brown con- 

 tents ; parenchyma with brown contents. Seed-coat showing in 

 surface section epidermal cells with undulate walls ; branching 

 parenchyma with greenish or brownish-yellow contents ; and an 

 inner epidermis of elongated cells. Endosperm having a layer 

 of cells containing aleurone grains, resembling those found in 

 the true cereals, and parenchyma with numerous angular or some- 

 what rounded or ellipsoidal starch grains (resembling those of 

 rice or oat), with distinct central cleft and varying from 5 to 12 ytt 

 in diameter (Fig. 138). 



