d to a heat of about 400 deg., or when
treated with sulphuric acid, or with a substance extracted from malt
called _diastase_, it is converted into dextrine. It may also be
obtained from cellulose by a similar treatment. The dextrine so obtained
has the same composition as the starch from which it is produced, but
its properties more nearly resemble those of gum. It plays a very
important part in the process of germination, and may be converted into
sugar on the one hand, and apparently also into starch on the other.

_Sugar._--Under this name are included four or five distinct substances,
of which the most important are, cane sugar, grape sugar, and the
uncrystallisable sugar found in many plants.

_Cane Sugar._--This variety of sugar, as its name implies, is found most
abundantly in the sugar cane, but it occurs also in the maple,
beet-root, and various species of palms, from all of which it is
extracted on the large scale. It is extremely soluble in water, and can
be obtained in large transparent prismatic crystals, as in common
sugar-candy. It swells up, and is converted into a brown substance
called caramel, when heated, and by contact with fermenting substances,
yields alcohol and carbonic acid. It contains--

Carbon 42.22
Hydrogen 6.60
Oxygen 51.18
------
100.00

and its chemical formula is C_{12}H_{11}O_{11}.

_Grape Sugar_ is met with in the grape, and most other fruits, as well
as in honey. It is produced artificially when starch is boiled for a
long time with sulphuric acid, or treated with a large quantity of
diastase. It is less soluble in water than cane sugar, and crystallises
in small round grains. Its composition, when dried at 284 deg., is--

Carbon 40.00
Hydrogen 6.66
Oxygen 53.34
------
100.00

and its formula is C_{12}H_{12}O_{12}; but when crystallised it contains
two equivalents of water, and is then represented by the formula
C_{12}H_{12}O_{12} + 2H_{2}O.

The uncrystallisable sugar of plants is closely allied to grape sugar,
and, so far as at present known, has the same composition, although,
from the difficulty of obtaining it quite free from crystallised sugar,
this is still uncertain.

_Mucilage_ is the name applied to the substance existing in linseed,
and in many other seeds, and which communicates to them the property of
swelling up and becoming gelatinous when treated with