[Illustration: _Convolvulus sepium_, slightly reduced.
1. Flower cut vertically. 2. Fruit, slightly reduced. 3. Seed cut lengthwise showing embryo. 4. Embryo taken out of seed. 5. Horizontal plan of arrangement of flower.]
The large showy flowers are visited by insects for the honey which is secreted by a ring-like disk below the ovary; large-flowered species of _Ipomaea_ with narrow tubes are adapted for the visits of honey-seeking birds.
The largest genus, _Ipomaea_, has about 400 species distributed throughout the warmer parts of the earth. _Convolvulus_ has about 150 to 200 species, mainly in temperate climates; the genus is principally developed in the Mediterranean area and western Asia. _Cuscuta_ contains nearly 100 species in the warmer and temperate regions; two 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.