A thank you to John B. (aka DCTropics@Flickr) for sharing these images of the staminate (male) and pistillate (female) flowers of Begonia hatacoa (original image 1 | original image 2 | via the Botany Photo of the Day Flickr Pool). Much appreciated, John. Do check out John's other begonia photographs.
Begonia hatacoa is native to Bhutan, Nepal and northern India, where it can be found in mid-elevation (1200m-1500m) broadleaf evergreen forests. As noted in the linked Flora of China profile, plants grow "on rocks in shaded moist environments on slopes or by streams".