About Cycnium tubulosum (L.fil.) Engl.
Cycnium tubulosum, commonly known as vlei ink-flower, is a hairless or nearly hairless hemiparasitic perennial herbaceous plant growing 12–60 cm tall. It has four-sided angular stems that are creeping, straggling, or upright; stems may have no side branches, and sometimes carry a few glandular hairs. Leaves are few, spaced apart, arranged oppositely or nearly oppositely; they are roughly linear, widest at midlength, with a pointed cartilaginous tip. Leaves have very short stalks or are stalkless, are glossy, have smooth margins or a few teeth, and are rather thick with sunken veins. They measure 2–8 cm long and 1–10 mm wide. Flowers are 1.75–3.25 cm long, with a shape similar to Phlox flowers. Each flower grows individually from the axil of a bract, on a slender but rigid stalk 0.75–2.5 cm long that has no additional bracts below the flower. The five sepals are fused into a bell- to cone-shaped calyx tube 0.8–1.3 cm long, marked with ten veins, ending in five almost lanceolate, keeled lobes that taper toward their tips and are 4–8 mm long. The corolla can be white, pinkish, or purple, made of five petals fused into a curved, cylindrical tube 1.6–2.8 cm long. Above the corolla limb, the structure forms an almost flat disk 0.75–4.25 cm in diameter, which divides into five ovate lobes with rounded margins. The two lobes on the outside of the corolla's curve are fused along a longer length than the other lobes. Inside the corolla tube are five stamens with softly hairy filaments, topped by hairless, oblong anthers 2 mm long. The style does not extend as far as the stamens, and is capped by a thickened, pointed stigma. The fruit is a hairless, short, oblique, slightly compressed oval capsule 0.5–1.25 cm long and wide, capped with a short, obliquely pointing beak, and has leathery valves. The entire plant turns black when dried for preservation. Vlei ink-flower has been recorded in Angola, Botswana, Eswatini, Ethiopia, Kenya, Madagascar, Malawi, Mozambique, Namibia, Nigeria, Rwanda, Somalia, South Africa, South Sudan, Tanzania, Uganda, Zaire, Zambia, and Zimbabwe. It grows in moist short grasslands, at altitudes up to around 1,550 m. The flowers of vlei ink-flower, which are white, rosy-tinged, or sometimes purple, open in the evening and have long narrow corolla tubes. These features are typical of hawkmoth-pollinated flowers, though no distinct scent has been observed. The moth species Hippotion celerio and Nephele comma have been recorded visiting C. tubulosum.
