Horse Chestnut Seed
I came upon a Horse Chestnut tree last autumn. Though their seeds have a superficial resemblance to the American Chestnut , there are lots of differences: American Chestnuts are in the same family as oaks and beeches, while Horse Chestnuts are in the same family as maples. American Chestnuts are native to much of North America; Horse Chestnuts are native to southern Europe. American Chestnuts are hard to find due to being devastated by chestnut blight; Horse Chestnuts in the US are not uncommon. While the seeds of American Chestnuts used to be a good food source for us and many other animals, Horse Chestnut seeds are poisonous to most birds/mammals. Here's the inner part of a Horse Chestnut seed. I'm assuming that wild animals know not to eat them despite them looking a bit like a cap-less acorn. I've read that these seeds are toxic when fresh but lose their toxicity when they start to germinate, and that crows and jays will sometimes bury them and then go back to eat them...