are native
in Britain.

The tubers of _Ipomaea Batatas_ are rich in starch and sugar, and, as
the "sweet potato," form one of the most widely distributed foods in the
warmer parts of the earth. Several members of the order are used
medicinally for the strong purging properties of the milky juice (latex)
which they contain; scammony is the dried latex from the underground
stem of _Convolvulus Scammonia_, a native of the Levant, while jalap is
the product of the tubercles of _Exogonium Purga_, a native of Mexico.
Species of _Ipomaea_ (morning glory), _Convolvulus_ and _Calystegia_ are
cultivated as ornamental plants. _Convolvulus arvensis_ (bindweed) is a
pest in fields and gardens on account of its wide-spreading underground
stem, and many of the dodders (_Cuscuta_) cause damage to crops.

CONVOY (through the Fr. from late Lat. _conviare_, to go along with,
from Lat. _cum_, with, and _via_, way; "convey" has the same ultimate
origin [see CONVEYANCE], neither word being connected, as has sometimes
been supposed, with Lat. _convehere_, to carry together), a verb and
noun now almost exclusively used in military and naval parlance. As a
verb it signifies in the first instance to accompany or to escort; and
in the 17th century we even hear of cavalry "convoying" infantry, but
its meaning was soon complicated by the growing use of the word "convey"
in the sense of "to carry," and as the usual task of an escort was that
of accompanying and protecting vehicles containing supplies, the noun
"convoy" (Fr. _convoi_) was introduced and has thenceforward in land
warfare meant a train of vehicles containing stores for the use of
troops and its guard or escort. Sometimes even the word is found in the
meaning of the train of vehicles without implying that there is an
escort, so far has the original meaning become obscured; but the idea of
military protection is always present, whether this protection is given
by a separate escort or provided by the weapons of the drivers
themselves.

In naval warfare the term is used to describe a method adopted for
defending merchant ships against capture. It was usually applied to the
vessels to be protected--as for example "the Baltic convoy," or "Captain
Montray's convoy." Until the 17th century the English term was "to waft"
and the warship employed to guard the traders on their way was called "a
wafter." The practice of sailing in convoy for mutual protection was
common in the middle ages