I have been having an experiment with some cheap extension tubes and an old 28-70 mm zoom lens from the Pentax ME Super. The lens is ideal as not only did it have a close focus function but unlike modern lenses (well most anyway) you can manually set the aperture. With cheap extension tubes there are no electronic connections to your lens so you are in full manual mode, with no control over the aperture.
The shot is looking into the throat of a recent Streptocarpus. Very forgiving plants they used to be a favourite for teaching how to take leaf cuttings, when I was teaching Rural Science.
As its common name, Cape Primrose, suggests it is native to South Africa and Madagascar. Obviously tender in this country it is purely a house plant, which is easy to grow, has a long flowering period and as an added bonus is very beautiful as well.