|Ooline tree at Gamilaroi Nature Reserve|
Cadellia is a monotypic genus of trees in the botanical family Surianaceae. The sole species, Cadellia pentastylis, commonly known as ooline, is a medium to large tree with bright green leaves and rough tile-pattern bark. It has rain forest origins dating from the Pleistocene Era when much of Australia was wetter than it is today. It grows on moderately fertile soils, preferably those suited for agriculture or pasture development. Due to extensive forest clearing, it is now considered a vulnerable plant in Australia.
The Cadellia tree grows to be about 10 m - rarely 25 m in height. It grows leaves that are alternate, undivided and obovate or "oval" in shape. From about October till December, the ooline tree also grows flowers that consist of five white petals, about 5–7 mm in length. To accompany the flowers, the ooline also grows a brownish, wrinkled fruit, that is surrounded by five red sepals at its base. This fruit is generally grown from November til December. The fruits edibility for humans is not stated.
Cadellia pentastylis is listed as vulnerable under the Australian Environment and Biodiversity Conservation Act 1999. Small and typically fragmented stands of Ooline may be found in scattered localities on the lower western slopes of Australia's great dividing range between latitudes of 24ºS to 30ºS. Populations are known from the North Western Slopes of NSW, such as around Tenterfield, Terry Hie Hie, Gunnedah and Moree. Ooline can also be found in Sundown National Park and Tregole National Park in Queensland.
The Cadellia is one of four sections of the Fables clade. Its pollen is prolate spheroidal, striate with a granular aperture surface membrane. Pollen morphology has linked the Surianaceae in a clade comprising Polygalaceae, Fabaceae, and Quillaja. There are also strong genetic affinities between the Mexican endemic genus Recchia and Cadellia. These can be determined by different types of micropscopy, such as; light microscopy, scanning electro microscopy, transmission electro microscopy. 
Black Orchids growing on Ooline - Tregole National Park
Stand of Cadellia pentastylis in Tregole National Park
- WOS:000227860100005 / Pollen morphology of families Quillajaceae and Surianaceae (Fabales)
- WOS:A1995TM23000006 / A reassessment of the familial affinity of the Mexican genus Recchia Mocino & Sesse ex DC
- PlantNET - The Plant Information Network System of Botanic Gardens Trust, Sydney, Australia
- Curran, T.J. & Curran, S.R. (2005). Rediscovery of Ooline, Cadellia pentastylis, near Gunnedah: notes on the habitat and ecology of this dry rainforest tree. Cunninghamia 9 (2): 311-316.
- Department of Environment & Climate Change New South Wales (2005), Ooline - Profile, Accessed 18 March 2009. http://www.threatenedspecies.environment.nsw.gov.au/tsprofile/profile.aspx?id=10118 .
- Department of the Environment, Water, Heritage and the Arts (2008). Cadellia pentastylis in Species Profile and Threats Database, Department of the Environment, Water, Heritage and the Arts, Canberra. Accessed 25/09/2008.
- Harden, G.J., McDonald, W.J.F. & Williams, J.B. (2006). Rainforest trees and shrubs: a field guide to their identification in Victoria, New South Wales and subtropical Queensland using vegetative features. Gwen Harden Publishing, Nambucca Heads, NSW.
- Herbrecs (2008). Cadellia pentastylis, in BriMapper version 2.12. Queensland Herbarium. Accessed 25/09/2008.
- Pollock, A.B. (1999). Cadellia pentastylis, in Species Management Manual. Department of Natural Resources, Brisbane.