at the expense of the
leaf; robbing it of its nourishment, and causing it to droop and to die.
A mixture of powdered lime and sulphur has been found to be an effective
germicide, if used in time and diligently applied.

[Illustration: Fig. 337. Coffee. Spermoderm in surface view. _st._
sclerenchyma; _p_, compressed parenchyma. x160. (Moeller)]

[Illustration: Fig. 338. Coffee. Cross-section of outer layers of
endosperm, showing knotty thickenings of cell walls. x160. (Moeller)]

[Illustration: Fig. 339. Coffee. Tissues of embryo in section. x160.
(Moeller)]

_Value of Microscopic Analysis_

The value of the microscopic analysis of coffee may not be apparent at
first sight; but when one realizes that in many cases the microscopic
examination is the only way to detect adulteration in coffee, its
importance at once becomes apparent. In many instances the chemical
analysis fails to get at the root of the trouble, and then the only
method to which the tester has recourse is the examination of the
suspected material under the scope. The mixing of chicory with coffee
has in the past been one of the commonest forms of adulteration. The
microscopic examination in this connection is the most reliable. The
coffee grain will have the appearance already described.
Microscopically, chicory shows numerous thin-walled parenchymatous
cells, lactiferous vessels, and sieve tubes with transverse plates.
There are also present large vessels with huge, well-defined pits.

[Illustration: COFFEE LEAF DISEASE (HEMILEIA VASTATRIX)

1. under surface of affected leaf, x 1/2; 2, section through same
showing mycelium, haustoria, and a spore-cluster; 3, a spore-cluster
seen from below; 4, a uredospore; 5, germinating uredospore; 6,
appressorial swellings at tips of germ-tubes; 7, infection through stoma
of leaf; 8, teleutospores; 9, teleutospore germinating with promycelium
and sporidia; 10, sporidia and their germination (2 after Zimmermann, 3
after Delacroix, 4-10 after Ward)]

Roasted date stones have been used as adulterants, and these can be
detected quite readily with the aid of the microscope, as they have a
very characteristic microscopic appearance. The epidermal cells are
almost oblong, while the parenchymatous cells are large, irregular and
contain large quantities of tannin.

Adulteration and adulterants are considered more fully in chapter XVII.

[Illustration: GREEN AND ROASTED COFFEE UNDER THE MICROSCOPE

Green bean, sho