That's actually interesting to me because it looks like a Pseudotsuga macrocarpa (northamericantrees.com), which occurs nowhere in the world but southern California.
Knowing your plants is an interesting way to asses the location of photographs/paintings. It's amazing how often you can tell when a movie or television show that's supposed to be in New York is actually in Los Angeles by the plants and trees you see in the background.
Maybe he was in the US at some point, he was in communication with Democrats talking about their eugenics programs. He was writing letters to Margaret Sanger for instance.
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