THE COCOA TREE AND ITS FRUIT 19 
tacles known as pigment cells, and ducts with spiral markings. . The 
starch grains do not have any very characteristic form or markings ; 
they are generally spherical and simple. The only peculiarity worth 
mentioning is the relative slowness with which they are acted upon 
by hot water and by iodine. The coloring substances are mainly of a 
carmine or violet color, and are distinguished by the change of shade 
when an alkali is added, becoming thereby darker. 
‘These are the only structural elements which a pure powder or 
paste of chocolate should show under the microscope. Any other 
substances must be recognized as accidental or intentional additions. 
All seeds of whatever kind contain, as a part of their substance, 
the matter of which cell walls are made, namely, cellulose. The 
percentage differs in different seeds, in those of the chocolate plant 
being about three in the hundred. Cellulose has the same chemical 
composition as starch, but its physical properties are not the same as 
those of starch; among these may be mentioned its entire insolu- 
bility in boiling water, whereas starch readily dissolves. 
Starch forms, on an average, 6 to 10 per cent. of chocolate seeds. 
It consists of minute spherical grains, not distinguishable from that 
found in many other kinds of seeds. Traces of gum and of other 
allied bodies are also present in the seeds. 
Albuminoids, or substances resembling, in a general way, the albu- 
men of egg, occur in chocolate seeds as they do in other seeds, 
and in a somewhat higher amount than in certain other cases in 
which seeds are used as food. The percentage ranges from about 
15 to 20, depending on the variety. These albuminoids are com- 
pounds of nitrogen, and are extremely nutritious. In the seeds they 
occur in a readily assimilable form, fit for digestion. 
Cacao red occurs as a coloring matter:in small amount. It is ren- 
dered dark by alkalies. oui er 
Theobromine, the active Biitigile of the cocoa bean, constitutes 
less than 1 per cent. of the weight of the seeds, but it varies greatly 
