THE COCOA BEAN VIEWED MICROSCOPICALLY. 947 
The cocoa bean is inclosed in a thin, brittle, reddish brown seed coat, 
- ealled the husk or shell. On the surface of the husk are often found 
numerous delicate, tubular cells, which come from the pulp of the fruit. 
The important structures of the husk proper are the following: 
(1) The epidermal layer. 
(2) The loose parenchyma. 
(5) The fiber bundles with small spiral cells. 
(4) The layer of characteristic thick-walled cells. 
After softening the husk by soaking the bean in water, a portion of 
the epidermal layer is readily torn away with the forceps, freed from 
adhering fragments of the adjacent tissue, and placed on the slide for 
examination. It is found to consist of a layer of moderately thick- 
walled, somewhat elongated, irregularly polygonal cells (see Plate 
XLVI). By careful dissection and careful manipulation of the light 
and the micrometer screw, a layer of exceedingly delicate, transversely 
elongated cells can be seen to lie directly under the layer just described, 
but it is so very delicate that it is rarely seen in the examinations of 
preparations of cocoa for adulterants, and is consequently of almost no 
importance in such investigations. If some of the underlying tissue 
exposed by the removal of the epidermis be transferred to a slide and 
dissected apart, it will appear as a mass of loosely aggregated, rather 
large, thin-walled, slightly elongated cells, those constituting the inner 
layers containing a large amount of mucilaginous matter that swells 
up in contact with water and ruptures them. This parenchymatous 
tissue, which makes up the greater part of the husk, is pierced in all 
directions by small, ramifying fiber bundles inclosing small spiral cells 
and stone cells; near the inner surface of the husk it is interrupted by 
a single layer of small, very thick-walled cells (see Plate xLv1), which 
are very characteristic and withstand the disintegrating processes 
of manufacture better than any other part of the husk. In fact, these 
processes are often carried so far that it is only by very diligent search 
that one is able to find any recognizable structures besides these cells 
and the starch grains of the cotyledons. For the detection of the 
presence of husks in cocoa preparations, these thick-walled cells are 
first sought for; and after these the epidermal and parenchymal struc- 
tures. The fiber bundles, with inclosed spiral cells, are not readily 
distinguished from those of the cotyledon. 
If the brown husk be entirely removed from the remaining part of 
the bean, a thin, transparent membrane will be observed, which partly 
comes away with the husk and partly remains adherent to the bean 
proper, dipping into all the clefts and plications of the latter. When 
a portion of this membrane is examined with the microscope, it appears 
as a Single layer of small polygonal cells which are filled with granular 
matter (see Plate XLvII). By careful manipulation one or more layers 
of parenchymatous cells can be found underneath the layer just de- 
scribed. Adherent to this membrane, especially to the folds entering 
the clefts of the cotyledons, are numerous yellow, club-shaped masses 
) 20393—No, 13——6 
