phototropism monitor

[mtg]

I have a phototropism monitor, almost antique, and I've forgotten how to use it. I know you wind it up and start it somehow and it then turns. The clear container on the top is to allow the sunlight to register......but on a little plant?, or what? It's by Griffin and George Ltd. London.

[smiley]

My father did his PhD on plants that move, so I grew up with all the windowsills in the house covered with various contraptions. Can you post a photo?

[mtg]

will try