Actually, this one is technically a Thanksgiving Cactus of the Schlumbergera truncata group, as opposed to the S. buckleyi group as shown by the pollen colour, leaf shape, and flower position.  See: http://en.wikipedia.org/wiki/Schlumbergera

We have a very large Christmas Cactus as well, my grandmother had it for years and it now has branches several feet long.  They are ideal house plants, not minding partial darkness, occasionally forgetful watering, and so forth.

Indoor plants are remarkably useful in a house, they add a living touch as well as potentially ornamental/sculptural effects.  They are also an innovation of the mid nineteenth century for the majority of the population, a combination of central heating and the colonization of the neo-tropical regions from which most houseplants hail, including the Christmas cactus group which comes from the coastal mountains of southeastern Brazil.  While the use of southern exposure and walled gardens to extend the growing season and to fiddle the garden’s zone one or two levels dates back to the Classical World, the idea of a Glass enclosed, heated environment wasn’t possible until the modern era.  That a house could have enough light and heat to grow plants which needed longer days and temperatures staying above fifty must have been a revelation for the frustrated gardener.