Hydnophytum
# Hydnophytum

Hydnophytum is a genus of epiphytic myrmecophytes (ant plants) native to Southeast Asia, the Pacific region and also extending into Queensland in northern Australia. The name is derived from the Ancient Greek hydnon "tuber", and phyton "plant", after their appearance with their swollen succulent stems. The species grow in tree branches and on trunks. Like the related genus Myrmecodia, they are known as antplants or ant-house plants. The type species is Hydnophytum formicarum from the Philippines. The genus contains 55 species, of which 44 are found in and around the island of New Guinea. Many are poorly known, with 11 known only from the holotype.

They form a symbiotic relationship with ants. Ant plants provide habitats for ant colonies high up into the forest canopy, protecting them from the elements and also predators because of the spines. Hollow, smooth-walled tunnels form within the caudex with external entrance holes, providing an above-ground home for ant colonies. Ants likewise provide defense for the plant and prevent tissue damage, swarming to defend their home if disturbed. Ant colonies also provide nutrients to the plants by leaving wastes within the tunnels inside the caudex. Special glands lining the tunnels then absorb nutriment for the plant. This symbiosis allows the plants to effectively gather nutrients (via the ants) from a much larger area than the roots ever could cover.

These plants can be grown in cultivation without the ant species being present. Two species seen occasionally in cultivation are Hydnophytum ferrugineum from the McIlwraith Ranges east of Coen on the Cape York Peninsula, and H. moseleyanum, also from Cape York. The former has a spiny swollen trunk while the latter has a smooth one.

Hydnophytum is one of five ant-plant genera in the family Rubiaceae, the others being Anthorrhiza, Myrmecodia, Myrmephytum, and Squamellaria.

## Species

The following list, which includes more than 90 species, is based on The Plant List and likely includes many synonyms. Matthew Jebb and Camilla Huxley recognise only 55 species in the genus.

* Hydnophytum agatifolium Valeton
* Hydnophytum albense Valeton
* Hydnophytum albertisii Becc.
* Hydnophytum alboviride Merr. & L.M.Perry
* Hydnophytum amboinense Becc.
* Hydnophytum amplifolium S.Moore
* Hydnophytum andamanense Becc.
* Hydnophytum angustifolium Merr.
* Hydnophytum archboldianum Merr. & L.M.Perry
* Hydnophytum borneanum Becc.
* Hydnophytum brachycladum Merr.
* Hydnophytum bracteatum Valeton
* Hydnophytum brassii S.Moore
* Hydnophytum buxifolium Merr. & L.M.Perry
* Hydnophytum caminiferum Wistuba, U.Zimm., Gronem. & Marwinski
* Hydnophytum camporum S.Moore
* Hydnophytum capitatum Valeton
* Hydnophytum confertifolium Merr. & L.M.Perry
* Hydnophytum contortum Merr. & L.M.Perry
* Hydnophytum cordifolium Valeton
* Hydnophytum coriaceum Becc.
* Hydnophytum costatum Drake
* Hydnophytum crassicaule P.Royen
* Hydnophytum crassifolium Becc.
* Hydnophytum cuneatum Valeton
* Hydnophytum decipiens Merr. & L.M.Perry
* Hydnophytum dipteropodum (K.Schum. & Lauterb.) Valeton
* Hydnophytum dolichophyllum Valeton
* Hydnophytum ellipticum Merr. & L.M.Perry
* Hydnophytum ferrugineum P.I.Forst.
* Hydnophytum forbesii Hook.f.
* Hydnophytum formicarum Jack
* Hydnophytum grandiflorum Becc.
* Hydnophytum grandifolium Valeton
* Hydnophytum guppyanum Becc.
* Hydnophytum hahlii Rech.
* Hydnophytum hellwigii Warb.
* Hydnophytum heterophyllum Merr. & L.M.Perry
* Hydnophytum inerme (Gaudich.) Bremek.
* Hydnophytum intermedium Elmer
* Hydnophytum kajewskii Merr. & L.M.Perry
* Hydnophytum kejense Becc.
* Hydnophytum kelelense Valeton
* Hydnophytum kochii Valeton
* Hydnophytum lanceolatum Miq.
* Hydnophytum laurifolium Warb.
* Hydnophytum lauterbachii Valeton
* Hydnophytum ledermannii Valeton
* Hydnophytum leytense Merr.
* Hydnophytum linearifolium Valeton
* Hydnophytum longiflorum A.Gray
* Hydnophytum longipes Merr. & L.M.Perry
* Hydnophytum longistylum Becc.
* Hydnophytum loranthifolium (Benth.) Becc.
* Hydnophytum lucidulum Valeton
* Hydnophytum macrophyllum Warb.
* Hydnophytum magnifolium Merr. & L.M.Perry
* Hydnophytum membranaceum Merr.
* Hydnophytum microphyllum Becc.
* Hydnophytum mindanaense Elmer
* Hydnophytum mindorense Merr.
* Hydnophytum montis-kani Valeton
* Hydnophytum moseleyanum Becc.
* Hydnophytum myrtifolium Merr. & L.M.Perry
* Hydnophytum nigrescens Merr. & L.M.Perry
* Hydnophytum nitidum Merr.
* Hydnophytum normale Becc.
* Hydnophytum oblongum (Benth.) Becc.
* Hydnophytum orbiculatum Elmer
* Hydnophytum ovatum Miq.
* Hydnophytum papuanum Becc.
* Hydnophytum parvifolium Valeton
* Hydnophytum petiolatum Becc.
* Hydnophytum philippinense Becc.
* Hydnophytum punamense Lauterb.
* Hydnophytum radicans Becc.
* Hydnophytum ramispinum Merr. & L.M.Perry
* Hydnophytum robustum Rech.
* Hydnophytum selebicum Becc.
* Hydnophytum simplex Becc.
* Hydnophytum spathulatum Valeton
* Hydnophytum stenophyllum Valeton
* Hydnophytum stewartii Fosberg
* Hydnophytum subfalcifolium Valeton
* Hydnophytum subnormale K.Schum.
* Hydnophytum subrotundum Valeton
* Hydnophytum subsessile Valeton
* Hydnophytum sumatranum Becc.
* Hydnophytum tetrapterum Becc.
* Hydnophytum tortuosum Becc.
* Hydnophytum vaccinifolium P.Royen
* Hydnophytum virgatum Valeton
* Hydnophytum vitis-idaea Merr. & L.M.Perry
* Hydnophytum wilkinsonii Horne ex Baker
* Hydnophytum zippelianum Becc.
