The most characteristic members of the order are twining plants with generally smooth heart-shaped leaves and large showy white or purple flowers, as, for instance, the greater bindweed of English hedges, Calystegia sepium, and many species of the genus Ipomaea, the largest of the order, including the "convolvulus major" of gardens, and morning glory.
The creeping or trailing type is a common one, as in the English bindweed (Convolvulus arvensis), which has also a tendency to climb, and Calystegia Soldanella, the sea-bindweed, the long creeping stem of which forms a sandbinder on English seashores; a widespread and efficient tropical sand-binder is Ipomaea Pes-Caprae.
Some importance attaches to the form of the pollen grains; the two principal forms are ellipsoidal with longitudinal bands forming the Convolvulus-type, and a spherical form with a spiny surface known as the Ipomaea-type.
The large showy flowers are visited by insects for the honey which is secreted by a ring-like disk below the ovary; large Convolvulus sepium, slightly reduced.
Convolvulus has about tso to 200 species, mainly in temperate climates; the genus is principally developed in the Mediterranean area and western Asia.
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 Scarnmonia, 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.
Stachys, sp. not identified Anagallis collina, Schousb Convolvulus tricolor, L.
Convolvulus tricolor atroviolacea: hardy, i ft., white, blue and yellow.
This is the Convolvulus minor of gardens.
Pharbitis hispida: hardy, 6 ft., various; the many-coloured twining Convolvulus major.
Among the nine hundred species of Solanum less than a dozen have this property of forming tubers, but similar growths are formed at the ends of the shoots of the common bramble, of Convolvulus sepium, of Helianthus tuberoses, the so-called Jerusalem artichoke, of Sagittaria, and other plants.
- Ovary of Polygonum Convolvulus in longitudinal section during fertilization.