74 ELEMENTS OF APPLIED MICROSCOPY. 
The general predominance of elongated cells, the presence 
of ladder-cells and milk-tubes, the absence of opaque 
masses of dark-brown tissue and of granular cell-contents 
make the picture very different from that obtained in the 
case of coffee. 
Various other roasted roots, radishes, carrots, etc., 
fruits such as figs and pears, with grains of diverse sorts 
are sometimes used as coffee substitutes. In Massachu- 
setts the following have been found: Roasted peas, beans, 
wheat, rye, oats, chicory, brown bread, pilot-bread, char- 
coal, red slate, bark, and dried pellets, the latter consist- 
ing of ground peas, pea-hulls, and cereals, held together 
with molasses. In each case the presence of peculiar 
cells, other than the simple ones characteristic of the 
coffee-bean, will reveal the sophistication. The ground- 
up seeds of the Leguminose, peas and pea-hulls, for 
example, are quite commonly present, and may be de- 
tected by the starch-grains described on p. 66, and by 
the outer layers of the hull, which from their parallel 
structure are known as the palisade cells. 
5. The Microscopic Structure of Mustard.—Mustard, 
as it usually comes to the market, is a mixture of the 
ground seeds of two closely related herbaceous plants, 
Brassica (Sinapis) alba and nigra. The structure, in 
both cases, is very similar, and if the entire seed be ground 
up and examined, three distinct cell types will be appa- 
rent. On the outside are several layers of large flat trans- 
parent thin-walled cells, some rounded and some polyg- 
onal, showing in glycerin faint concentric markings 
about a median area (c and d, Fig. 30). These epider- 
