76 ELEMENTS OF APPLIED MICROSCOPY. 
bulk of the sample should be made up of the inner cell- 
contents. If an excess of the outer layers be present, it 
is evident that mustard-hulls have been added; and this 
is one of the commonest adulterations to which this sub- 
stance is subjected. Wheat- and rice-starch are also 
found not uncommonly, and furnish conclusive evidence 
of sophistication. Yellow aniline dyes are sometimes 
used to give the proper color to such adulterated samples. 
Turmeric, which is the ground rhizome of Curcuma 
longa, is also well adapted for the adulteration of mus- 
tard. It appears under the microscope in small amor- 
phous, intensely yellow, pasty masses, which stain blue 
with iodin, being made up largely of curcuma-starch. 
7. The Microscopic Structure of Pepper.—Pepper is 
the pulverized seed of Piper nigrum, a shrub cultivated 
mainly in the East Indian islands. The dried seed is 
about 5 millimeters in diameter and is covered with a 
brownish hull. If this hull is ground up with the grain, 
we have the ordinary black pepper. White pepper is 
made by macerating the fruit in water before drying, and 
detaching the hulls by friction. 
In ground black pepper a number of tissues may be 
made out, since the many-layered hulls are relatively 
thick as compared with the more homogeneous central 
portion. The latter forms the bulk of the preparation, 
and is quite characteristic in appearance. It consists of 
irregularly angular whitish masses, seen to be made up 
of polygonal cells packed full of very minute starch- 
grains (s and ss, Fig. 31). With a high power these 
grains themselves appear polygonal and closely aggre- 
