790 BOTANY AND PHARMACOGNOSY. 



a Do Not Readily Dissolve or Swell in Cold Water. 



236. CORN MEAL is whitish or yellowish, and in addition 

 to the parenchyma which contains oil and characteristic starch 

 grains there are also present fragments of the pericarp. The 

 latter are free from hairs ; the cells of the epicarp have thick walls 

 with simple pores ; beneath the latter occurs a layer of paren- 

 chyma cells which are thin-walled, more or less branching, between 

 which are large intercellular spaces ; running at right angles across 

 the branching parenchyma cells are narrow, thin-walled tube cells, 

 which are also found in the other cereals. Corn Meal contains 

 more starch and oil and little hull, as compared to corn bran. 

 In Broom Corn and Sugar Sorghum the tangential walls of the 

 cells of the epicarp are undulate and distinctly porous; and the 

 more or less polygonal cells of the perisperm are quite prominent. 

 These two kinds of cells serve to distinguish these fruits from 

 either corn or any of the other cereals. 



237. CORN BRAN. — Less starch and oil and more hull, as 

 compared to cornmeal. (See No. 236.) 



238. WHEAT FLOUR.— Agglutinates with water (distinc- 

 tion from wheat starch) ; little tissue of wheat grain. (See No. 



239) 



239. WHEAT MIDDLINGS are grayish-white and in addi- 

 tion to the characteristic starch grains (Figs. 95; 97; 316, C) 

 there are numerous fragments of tissues, as the thick-walled poly- 

 gonal cells of the endosperm, which contain small aleurone grains 

 and have a more or less distinct nucleus ; the cells of the embryo 

 containing aleurone grains and fixed oil ; and the tissues of the 

 pericarp. The latter include unicellular hairs, which are 0.5 to i 

 mm. in length and 15 to 25 /* in diameter, have a sharply pointed 

 apex and rounded base, and a narrow lumen, which is but i or 2 /t 

 wide ; a layer of tangentially elongated cells from 100 to 200 n 

 long and 15 to 25 /t in diameter, which are slightly thickened and 

 with simple pores ; and running across the latter are a number of 

 more or less isolated vermiform cells with rounded ends. 



Wheat bran is said to be sometimes adulterated with " inner 

 coffee hulls," which consist of the inner tissues of the pericarp of 

 the coffee fruit (see No. 154), and are readily detected by the 



