Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Rosales
Family: Urticaceae
Botanical name: Elatostema rugosum
Common name: Parataniwha, Native begonia, winkled elatostema, New Zealand Begonia,  Parataniwhaniwha.

Parataniwha is a member of the nettle family. It is a herbaceous ground cover plant and is one of our very few perennials. It grows up to at 1m tall in wet shaded areas such as damp shady streamsides and gullies. It can form large colonies and is often the dominant groundcover vegetation. It has large prominently veined bronze green leaves (8-25 cm long) with purple tonings. The distinctive rough leaves give rise to the taniwha part of the common name because of taniwha in Maori means shark. (After the sharks rough skin)
Parataniwhais is found naturally only in the North Island.

Photo below is of a patch of burnished purple-red Elatostemma rugosum  which must get just enough sun to turn the leaves this rich colour, whereas the patch in a lower photo is in complete shade and is green in colour.
Photographed at Burgess Park, New Plymouth.Elatostema rugosum Parataniwha-001.JPG 

Elatostema rugosum Parataniwha-003.JPG

A young plant with small male flowers appearing on glomerules/
Elatostema rugosum Parataniwha NZ Begonia.JPG

Young glomerules are fleshy pads of tissue, each containing a large number of developing flowers. Glomerules are 0.5-30 mm in diameter when matue. Flowers are unisexual and may be mixed in the same glomerule.

Elatostema rugosum Parataniwha -001.JPG

Elatostema rugosum Parataniwha NZ Begonia-003.JPG 
The hyaline ((Gr. hyaleos: transparent) male flowers are 1-3 mm in diameter and consist of four translucent tepals and stamens. The stalk (filament) of each stamen is curled tightly like a watch-spring in the bud and springs open when the anther is mature. 
Elatostema rugosum Parataniwha -002.JPG

Elatostema rugosum Parataniwha .JPG

A young leaf.
Elatostema rugosum Parataniwha NZ Begonia-002.JPG

A leaf's upper blistered surface with raised and recessed areas and widely spaced hairs.  These hairs are multicellular, unbranched and taper from the base to the tip.Elatostema rugosum Parataniwha NZ Begonia-002.JPG

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