Thismia rodwayi

Thismia rodwayi is, as botanist Mark Wapstra puts it, 'aptly described' by its common name: fairy lantern.[3] It is a very small flower, only visible as an orange and red obovate floral tube of 10 to 18 mm in length. This flower is surmounted by six perianth lobes: three inner lobes curving inward, and three outer ones spreading outward.[2]

The flower lies atop a 0.5 to 3 cm long colourless and subterranean flower stem which bears six bracts, increasing in size toward the flower. The flower stem arises from the juncture of the 1 to 1.5 mm thick and 4 to 15 cm long roots.[2]

Each individual plant usually produces only one flower per bloom cycle, occasionally two; plants can be found in groups of 2 to 5 (and up to 12) in an area of less than 1 m².[1]

Thismia rodwayi in bud.

Thismia rodwayi occurs in wet eucalyptus forests, mainly Eucalyptus obliqua, E. regnans, E. delegatensis and E. viminalis, between 100 and 650 m above sea level.[1] The potential habitat in Tasmania is estimated with the RFA (Regional Forest Agreement), such as "tall E. obliqua forest" (OT) or "wet E. viminalis forest" (VW).[3] As occurrence data for the species are sparse, the potential habitat is much more widespread than the flower itself.[1]

On a local scale, potential Thismia areas are identified by a sparse canopy cover, and a damp, dense and cohesive topsoil with a thick litterfall.[4]

Thismia rodwayi's life cycle is still very poorly understood.[1] As it usually appears in patches of closely situated individuals, it is generally accepted that both pollen and seeds are transported only short distances, which could explain why the plant occurs in only a fraction of its potential habitat.[4]

There currently exist two main hypotheses concerning the mechanisms of Thismia rodwayi's pollination:

• Entomophily: Fungus gnats could be constrained inside the floral tube, and be forced to exit through the gaps between the anthers, thus coating themselves in pollen.[5]
• Zoophily: Mammals such as the potoroo (Potorous tridactylus) are known to feed on roots and subterranean fungus in similar habitats and could serve as pollinators. Another possible vector could be the superb lyrebird (Menura novaehollandiae).[1]

Vegetative expansion by stolons is also considered a possibility.[4]

Although earlier[2][6] regarded as a saprophyte, Thismia rodwayi is actually a mycoheterotroph, a non-chlorophyllous plant associated with a truly saprophytic fungus. The fungal hyphae are found in the cortical cells of the plant's roots, and also around those roots.

Nutrients in rotting organic material are absorbed by the fungus and stocked as fat globules in the hyphal bladders of the fungus. The hyphal cells are then induced to discharge the fat globules into the cells of the plant, where they are turned into a polysaccharide, possibly glycogen.[1]