On the Nature and Causes of the Decay in Potatoes. 535 
of a somewhat spherical shape, and are composed of a mucous 
substance, which is white and transparent {vide Fig. I., in which 
Fig. I. 
the cells are darkened to represent the disease). Within these 
cells are placed other little globules which measure usually about 
the -^i^^ of an inch in diameter. These little globules are the 
starch or fecula of the potato. They are of different sizes and 
shapes, but they may be compared to the form of a flask. These 
globules of starch are made up of concentric layers — that is, one 
layer laid upon another, and at one part of each globule is the 
hilum or point of attachment to the walls of the cell, from which 
they become detached as others are formed. 
The physiologist contents himself with the anatomical examina- 
tion of the potato, and the chemist then comes to tell us more 
minutely about the ingredients contained in it. It is a thousand 
pities that they have not gone hand in hand in their examination. 
Their combined knowledge tells us that the little globules in the 
cells consist of starch ; but then there are many other substances in 
the potato to which we do not know where to assign a habitation. 
For example, there is sugar ; but we are ignorant of its exact 
position in the tuber. Keasoning from what is known as to its 
position in other vegetables, we must assume that it likewise is 
situated in cells. Then there is albumen, the same as exists in 
the white of an egg : this probably also is contained in the cellular 
sap, and sometimes cheese is also to be detected therein, according 
to the statement of Liebig, Gluten, the same as that in corn, also 
exists in the potato ; and this being insoluble, is doubtless placed 
as it is in the cereals, to aid in forming the cellular tissue. Gum 
is also present : perhaps along with the sugar it may be in solu- 
tion in the cellular water surrounding the globules of starch. 
Starch is undoubtedly the most important constituent, and that 
which is truly the characteristic of the potato. The tuber may, 
as an average result, be viewed as composed of 74 lbs. of water, 
8 lbs. of skin and fibrous matter, 16 lbs. of starch, and 2 lbs. of 
