There is a citrus tree growing in the yard at the office. The fruits are oranges, but very weird oranges -- they never get orange. They stay green and when over-ripe turn brown, with a very brittle skin. When they are ripe, the skin is hard and thick but not dried brittle when you leave them too long on the tree.
I was perplexed by these things. We had a crop of them in December, and now we have a new bunch. All of the fruit disappeared after the Haitian house painters went through the yard. I actually peeled and ate one. The fruit was seedy and kind of dry, but it had more pucker power than sour candy sucked through a straw. The aftertaste of citrus acid lingered for a long time. It was an acquired taste, and I could see myself eating more, but the painters beat me to it.
When the new crop appeared on the tree, I eagerly picked one. It was green, or should I say unripe, and tough to peel. I had to use my teeth to crack the peel, and the spurt of acid caused a coughing jag that wouldn't quit and my eyes were burning. When unripe it is both a chemical and lethal weapon. The acid actually burned my mouth.
I tried to Google this variety of citrus but was unsuccessful. The woman who knew the history of this place came by and told me that the tree was once a sweet orange tree grafted onto a sour or Cuban orange root. Eventually the sweet orange graft died after many many years, and a new shoot appeared out of the root, reverting back to sour or Cuban oranges. It is perhaps fitting that the Cuban orange is a sour one.