The Families of Flowering Plants
The Families of Flowering Plants | |
~ Convolvulaceae
Habit and leaf form. Parasitic herbs. Plants of very peculiar vegetative form; filamentous (with threadlike, chlorophyll-less twining stems and short-lived root systems). Leaves much reduced. Plants rootless (in that the normal root system is ephemeral); totally parasitic. Parasitic on aerial parts of the host. With neither basal nor terminal aggregations of leaves. Climbing; stem twiners (with haustoria). Leaves minute; alternate; spiral; membranous; sessile; non-sheathing; simple; epulvinate. Lamina entire. Leaves exstipulate.
Leaf anatomy. Minor leaf veins without phloem transfer cells.
Stem anatomy. Primary vascular tissue centrifugal. Secondary thickening absent. Xylem with vessels. Vessel end-walls simple.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers small; regular; (3–)5 merous; cyclic; tetracyclic. Free hypanthium absent.
Perianth with distinct calyx and corolla; 6, or 10; 2 whorled; isomerous. Calyx (3–)5; 1 whorled; gamosepalous; imbricate. Corolla (3–)5; 1 whorled; appendiculate (with lobed or fringed scales alternating with the stamens); gamopetalous; valvate; regular; white, or pink.
Androecium 5, or 10 (if the scales alternating with the stamens are interpreted as staminodes). Androecial members adnate (to the corolla tube); free of one another; 1 whorled, or 2 whorled (i.e. including the scales). Androecium exclusively of fertile stamens, or including staminodes (in the form of lobed or fimbriate scales). Staminodes 5; internal to the fertile stamens (antepetalous). Stamens 5; inserted in the throat of the corolla tube; isomerous with the perianth; oppositisepalous. Anthers dehiscing via longitudinal slits; tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer; of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate; 3–6 aperturate; colpate (including rupate); 3-celled.
Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary 2 locular. Styles 2; free, or partially joined; apical. Stigmas dry type; papillate; Group II type. Placentation basal. Ovules 2 per locule; ascending; anatropous; unitegmic; tenuinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Synergids beaked; haustorial (sometimes?), or non-haustorial. Endosperm formation nuclear. Embryogeny caryophyllad to solanad.
Fruit non-fleshy, or fleshy; dehiscent; a capsule. Capsules splitting irregularly (or opening by a transverse slit). Seeds endospermic. Endosperm oily. Embryo rudimentary at the time of seed release to weakly differentiated (filiform). Cotyledons 0 (or scarcely recognisable as such). Embryo chlorophyllous (1/4); curved, or coiled, or other than straight, curved, bent or coiled (spiral).
Seedling. Germination type inapplicable in the absence of cotyledons.
Physiology, biochemistry. Cyanogenic (?), or not cyanogenic. Iridoids not detected. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent. Saponins/sapogenins present, or absent.
Geography, cytology. Temperate to tropical. Cosmopolitan. Chromosomes with diffuse centromeres. X = 7, 15.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Solaniflorae; Solanales. Cronquist’s Subclass Asteridae; Solanales. APG (1998) Eudicot; core Eudicot; Asterid; Euasterid I; Solanales (as a synonym of Convolvulaceae). Species 170. Genera 1; only genus, Cuscuta.
Illustrations. • Cuscuta epithymum (on Calluna). • Technical details (Cuscuta). • Technical details (Cuscuta).
This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting specified attributes, summaries of attributes within groups of taxa, geographical distribution, genera included in each family, classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG), and notes on the APG classification.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 10th April 2008. http://delta-intkey.com’.
