e same
plant they are generally so much alike as to admit of their recognition
by a practised observer. They were formerly believed to be composed of
an external coating of a substance insoluble in water, and containing in
their interior a soluble kernel; but this opinion has been refuted, and
distinct evidence been brought to show that the exterior and interior of
the globules are identical in chemical properties. Starch is insoluble
in cold water, but by boiling, it dissolves, forming a thick paste. By
long continued boiling with water containing a small quantity of acid,
it is completely dissolved and converted into dextrine, and eventually
into sugar. The same change is produced by the action of fermenting
substances, such as the extract of malt; when heated in the dry state to
a temperature of about 390 Fahr., it becomes soluble in cold water. It
is distinguished by giving a brilliant blue compound with iodine. Starch
contains--

Carbon 44.47
Hydrogen 6.28
Oxygen 49.25
------
100.00

and its composition is represented by the formula C_{12}H_{10}O_{10}, so
that it differs but little from cellulose in composition, although its
chemical functions in the plant are extremely different. It is connected
with some of the most important changes which occur in the growing
plants, and by a series of remarkable transformations is converted into
sugar and other important compounds.

_Lichen Starch_ is found in most species of lichens, and is
distinguished from common starch by producing a green colour with
iodine. Its composition is the same as that of ordinary starch.

_Inuline._--The species of starch to which this name is given is
characterised by its dissolving in boiling water, and giving a white
pulverulent deposit in cooling. It is found in the tuber of the dahlia,
in the dandelion, and some other plants. Its composition is identical
with that of cellulose, and its formula is C_{24}H_{21}O_{21}.

_Gum_ is excreted from various plants as a thick fluid, which dries up
into transparent masses. Its composition is identical with that of
starch. It dissolves readily in cold water, and is converted into sugar
by long continued boiling with acids. Its properties are best marked in
gum arabic, which is obtained from various species of acacia; that from
other plants differs to some extent, although its chemical composition
is the same.

_Dextrine._--When starch is expose