The usual varieties that you come across are 'Easter Cactus' and
'Christmas Cactus'. I am not exactly sure of their botanical names; I
think they are either Rhipsalidopsis, Schlumbergera or Zygocactus.
Names change from time to time. Anyway, hybrids are available and the
flowers range from pink to scarlet and also some orangey tones. I
believe they are all rain forest type cacti - living in nooks in tree
trunks etc. - so they are generally happy having their roots confined.