Korthalsella, commonly known as korthal mistletoes, is a genus of about 25 species of hemiparasitic flowering plants in the sandalwood family Santalaceae (order Santalales). The genus was formerly placed in the segregate family Viscaceae, and some treatments still retain that placement, but modern molecular work aligns it within Santalaceae.
Plants in the genus are subshrubs or herbs with a succulent, jointed habit. Leaves are reduced to vestigial scales — each pair fused into a collar encircling the constricted node, at first concealing the tiny flowers. This leafless, segmented appearance gives the plants a superficial resemblance to some chenopods or jointed-rush relatives, and in New Zealand they are simply called mistletoes. Flowers are minute and grouped in the leaf-axils at each node, with two clusters per node in New Zealand species (one male flower and four female flowers). Male flowers have three triangular, valvate tepals and stamens fused into a globe-shaped synandrium with six chambers opening inward to a central channel. Female flowers share the three-tepalled structure with an inferior ovary. Fruits are clavate to pear-shaped, somewhat succulent and sticky (viscid), with the tepals persisting at the tip.
Like other members of Santalales, Korthalsella species are obligate aerial hemiparasites, attaching to a wide range of host trees and shrubs via haustoria. The genus is distributed across Asia, Africa, Australia, New Zealand, and several Pacific Islands. In New Zealand, three species are endemic (K. clavata, K. lindsayi, K. salicornioides); the genus is treated as indigenous but non-endemic at the national level. Korthalsella japonica is the most broadly distributed species, occurring from Japan through Southeast Asia into the Pacific.
Etymology
Korthalsella was named in honour of Pieter Willem Korthals (1807–1892), a Dutch botanist who collected extensively in the Dutch East Indies (now Indonesia) during the 1830s. The genus was formally described by the French botanist Philippe Édouard Léon Van Tieghem in 1896, published in the Bulletin de la Société Botanique de France.
Distribution
The genus spans a broad range across the Old World and Pacific: Asia (including Japan and Southeast Asia), Africa, Australia, New Zealand, and various Pacific Islands. In New Zealand, three species are endemic and the genus is classified as indigenous (non-endemic). Korthalsella japonica has the widest individual range among the species.
Ecology
Korthalsella species are aerial hemiparasites that attach to woody host plants via haustorial connections, drawing water and nutrients from host tissue while retaining some photosynthetic capacity of their own. They parasitise a wide range of host tree and shrub species. The sticky, viscid fruits facilitate seed dispersal by birds, which inadvertently deposit seeds onto host branches.
Taxonomy Notes
The genus has historically been placed in Viscaceae (the mistletoe family) as well as Santalaceae. Current treatments — including GBIF's Santalaceae backbone and the Flora of New Zealand — place it in Santalaceae sensu lato, consistent with the APG circumscription that sinks Viscaceae into Santalaceae. Some regional checklists (e.g. the Flora of Australia, 1984) retain the Viscaceae placement. The genus was erected by Van Tieghem (1896); authorship is abbreviated Tiegh. in nomenclatural references.
