Christmas Cactus.

I have recently acquired a Christmas Cactus (really, I'm plant-sitting, but it's taking up enough of my kitchen.. this thing is huge!) and it seems to be happy. Over the past week, it's started churning out buds, and some of them have opened into gorgeous orange blossoms.

Like this one.

The flowers of a Christmas Cactus are specially adapted for specific pollinators. Nectar is produced and stored in a chamber at the base of the bloom, which is very long. A hummingbird must stick it's long beak down the flower to get at the nectar, and while doing so will brush it's head against the pollen covered stamens sticking out of the flower. Pollen from another plant will be deposited on the bright pink stigma from the top of the bird's head.

Side view.