Zygo cactus or Schlumbergera russelliana

"Schlumbergera russelliana" is a species of plant in the family Cactaceae. It is endemic to a small area of the coastal mountains of south-eastern Brazil where its natural habitat is moist forest. It grows on trees as an epiphyte. It is one of the parents of many of the popular houseplants known as Christmas cactus or Thanksgiving cactus.