Kingdom: Plantae
Unranked): Angiosperms
(Unranked): Eudicots
(Unranked): Asterids
Order: Apiales
Family: Pennantiaceae (or Icacinaceae)
Genus: Pennantia
Species: P. baylisiana
Binomial name: Pennantia baylisiana
Synonym:  Plectomirtha baylisiana
Common name: Three Kings Kaikomako

Pennantia baylisiana is a critically endangered species of plant in the Pennantiaceae family (Icacinaceae in older classifications). It is endemic to the Great Island (Manawa Tawhi), Three Kings Islands, New Zealand, where only one plant is known to exist. It is threatened by habitat loss. Pennantia baylisiana was once listed as one of the world's rarest plants by The Guinness Book of Records. The single tree known in the wild grows on a scree slope on the northern face of Great Island in the Three Kings group off Cape Reinga, New Zealand. It was discovered during a hunting exercise to rid the islands of goats. Professor Geoff Baylis of the University of Otago found both it in 1945. It had been reduced by the goats' foraging to a single specimen. It is still alive today some 65 years later, and has not produced any seedlings on the islands. Cuttings from the tree were taken to the Government research station at Mt Albert. The tree is functionally a female and as such did not produce any seed. Forty years after the Pennantia was found Ross Beever (1946-2010) a scientist with Landcare Research determined to try some experiments to see if he could induce it to produce seed. He was successful and the resulting seedlings have proved to be more fertile than their mother. From having been the rarest tree in the world (Guinness Book of Records) it is now widespread in cultivation, and Oratia Native Plant Nursery which assisted Ross in his project, now donates all the proceeds from the sale of Pennantias to help fund botanical research and to minimise the risk of extinction of other species.
The first seedlings of Pennantia baylisiana were sold at the Ellerslie Flower Show in 2002 at a premium price with all profits going to three conservation groups.
 A tree is growing in Pukekura Park, New Plymouth.

Pennantia baylisiana is a sturdy, multi-trunked tree 5-8 x 4 m tall with large, roundest, dark green, leathery, smooth, leaves. On shaded plants, the leaves the leaves are flat while plants in the sun have smaller leaves and these are strongly rolled under at the margins.

For more details of Pennantia baylisiana  http://nzpcn.org.nz/flora_details.asp?ID=32

Photographed at Otari Native Botanic Garden and Wilton's Bush Reserve. Wellington.
[1]

[2] 

The multi trunks of Pennantia baylisiana
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These leaves which are in the sun are strongly rolled under at the margins.
[4]

The surface of the leaf 
[5]

The undersurface of a leaf
  

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/