I found something very familiar in Rwanda - 石栗. It is that big tree behind me.
It produces a fruit with a thick skin. Inside is a nut with a hard shell, which looks somewhat like a chestnut.
Inside the hard shell is a whitish flesh. It tastes a little like walnut. That is perhaps why it is also called Indian walnut.
I remember it well. It is quite common in Hong Kong. When I was in secondary school, one day a classmate introduced us to the nut. We felt we found a treasure - a delicacy that costs nothing. I ate several, perhaps 6 or 7. That evening I had to go to the school clinic because of bellyache - together with several other classmates. We recovered. But I have had an aversion to walnuts ever since.
Later I found out that it is edible in small volumes. In some places people do eat them. It is poisonous if too much is eaten. It is very rich in oil, which can be processed into many uses, such as soap, paint and candles. That’s probably why it is also called candlenut.
It may be one of the reasons why I like Rwanda so much.