3. Cuscuta L. (dodder, love vine)
(Yuncker, 1943)
Plants parasitic
on the aboveground portions of other plants. Stems twining, glabrous, greenish
yellow, yellow, or orange, often forming tangled mats and attaching to host
tissues by suckerlike haustoria. Leaves alternate, consisting of small,
lanceolate or ovate, sessile scales 1–4 mm long. Inflorescences sessile or
stalked clusters along stems, sometimes appearing as small panicles. Flowers
with the surface smooth or densely and minutely papillose (warty or bumpy),
sometimes also with scattered resinous (pellucid-glandular) cells. Calyces 3–5(6)-lobed,
sometimes deeply divided to form separate sepals. Corollas white, rarely
greenish, 3–5(6)-lobed, the lobes erect to recurved, the tips sometimes
incurved. Stamens with a scalelike appendage (infrastaminal scale) attached to
the corolla tube below the attachment point of the filament, this infrastaminal
scale with a toothed or fringed margin. Ovary 2-locular. Styles 2, each with a
capitate (linear elsewhere) stigma. Fruits papery-walled capsules, usually with
an aperture between stigmas, breaking open irregularly (with circumscissile
dehiscence elsewhere). Seeds usually 2–4 per fruit, brown. About 145 species.
Nearly worldwide.
Contrary to some
reports, Cuscuta species do produce chlorophyll, although in reduced
quantities. Some species of dodder are important agricultural pests and have
been spread as contaminants in crop seeds. Species identification in the genus
is challenging and requires a hand lens. Details of the flowers are easiest to
observe in fresh specimens or in plants that have been dried without pressing.
Most dodders parasitize a wide variety of host species, and determination of
the host is usually not an aid in Cuscuta identification.