Photo by Ron Myhr
Grown at Royal Botanic Garden, Edinburgh
A. radicans usually has calyces that are more greenish and pale than appears to be the case in this photo. It is native to Thailand, Singapore, Malaysia and Indonesia. Other images of this species can be seen here and here.
Recently, a number of formerly separate species have been merged into A. radicans, including A. lobbianus and A. javanicus.