ameter. Most of the starch
granules are marked by a series of concentric rings. Starch is heavier
than water, and is insoluble in that fluid when cold; neither is it
dissolved by alcohol or ether. When heated in water having a temperature
of at least 140 deg. Fahrenheit, it increases greatly in volume, and
acquires a gelatinous consistence. When the water is allowed to cool,
a portion of the starch becomes insoluble, whilst another portion
remains in solution; the latter form of starch is sometimes termed
_amidin_, from the French word for starch, _amidon_. When dry starch
is heated to 400 deg. Fahr., it is converted, without any change in its
composition, into a soluble gum-like substance, termed _dextrin_,
or British gum. On being boiled in diluted sulphuric acid it is
converted into a kind of sugar; and the same effect is produced by
fermentation--for example, in the germination of seeds. Fresh rice
contains 82, wheat 60, and potatoes 20 per cent. of starch. This
substance constitutes a nutritious and easily digestible food, but
alone cannot support life. Arrowroot is only a pure form of starch.

_Sugar_ occurs less abundantly in plants than starch. There are several
varieties of this substance, of which the kinds termed cane sugar
(_sucrose_) and grape sugar (_glucose_), are only of importance to
agriculturists. The former enters largely into the composition of the
sugar-cane, the beetroot, the sugar-maple, the sorgho grass, pumpkins,
carrots, and a great variety of other plants. Grape sugar is found in
fruits, especially when dried--raisins and figs--in malted corn, and
in honey. In the sugar-cane there is 18 per cent., and in the beetroot
10 per cent. of sugar.

_Cane sugar_, when pure, consists of minute transparent crystals. It is
1-6/10 heavier than water, and is soluble in one-third of its weight
of that fluid. By long-continued boiling in water it is changed into
uncrystallizable sugar, or treacle, by which its flavor is altered, but
its sweetening power increased.

_Grape sugar_ crystallizes in very small cubes, of inferior color as
compared with cane sugar crystals. It dissolves in its own weight of
water, being three times less soluble than sucrose. In sweetening power
one part of cane sugar is equal to 2-1/2 parts of grape sugar; but there
is probably little if any difference, between the nutritive power of the
two substances.

_Inulin_ is a substance somewhat resembling starch. It does not occur
in