enchyma forms an uninterrupted covering in the early stages of the
seed; but as the seed develops, surrounding tissues grow more rapidly
than the sclerenchyma, and the cells are pushed apart and scattered. The
cells occurring in the cleft of the berry are straight, narrow, and
long, becoming as long as 1 mm, and resemble bast fibers somewhat. On
the surface of the berry, and sometimes in the cleft, there are found
smaller, thicker cells, which are irregular in outline, club-shaped and
vermiform types predominating.

Parenchyma cells form the remainder of the spermoderm; and these are
partially obliterated, so that the structure is not easily seen,
appearing almost like a solid membrane. The raphe runs through the
parenchyma found in the cleft of the berry.

The endosperm (Figs. 333; 338) consist of small cells in the outer part,
and large cells, frequently as thick as 100 mu, in the inner part. The
cell walls are thickened and knotted. Certain of the inner cells have
mucilaginous walls which when treated with water disappear, leaving only
the middle lamellae, which gives the section a peculiar appearance. The
cells contain no starch, the reserve food supply being stored cellulose,
protein, and aleurone grains. Various investigators report the presence
of sugar, tannin, iron, salts, and caffein.

The embryo (Fig. 331, III) may be obtained by soaking the bean in water
for several hours, cutting through the cleft and carefully breaking
apart the endosperm. If it is now soaked in diluted alkali, the embryo
protrudes through the lower end of the endosperm. It is then cleared in
alkali, or in chloral hydrate. The cotyledons shown have three pairs of
veins, which are slightly netted. The radicle is blunt and is about 3/4
mm in length, while the cotyledons are 1/2 mm long.

[Illustration: Fig. 336. Coffee. Sclerenchyma fibers of endocarp. x160.
(Moeller)]

_The Coffee-Leaf Disease_

The coffee tree has many pests and diseases; but the disease most feared
by planters is that generally referred to as the coffee-leaf disease,
and by this is meant the fungoid _Hemileia vastatrix_, which as told in
chapter XV, destroyed Ceylon's once prosperous coffee industry. As it
has since been found in nearly all coffee-producing countries, it has
become a nightmare in the dreams of all coffee planters. The microscope
shows how the spores of this dreaded fungus, carried by the winds upon a
leaf of the coffee tree, proceed to germinate