Another Cactus in Flower

This evening's blip shows two cacti on my windowsill. The one on the right is currently in flower. The long stalk extends from somewhere in the middle of the cactus for around 2 feet into the air. On the branches there are small white flowers.
I think that people often regard cacti now as a bit dull and uninteresting., which is a shame. It's really quite exotic to have something in the house which is native to a very different environment.