Below is a picture on leaves from a small American Chestnut (Castanea dentata) tree seen on the Lake Minnewaska nature walk I referenced in my previous witch-hazel post. Castanea means "chestnut" and dentata ("toothed") refers to the distinctive saw-tooth leaves.
All chestnut trees around here are relatively small, unfortunately, since they are usually killed by the chestnut blight fungus (Cryphonectria parasitica) before they have the chance to get too large. Right behind this small chestnut tree was a 20 foot high dead trunk - probably its parent tree (this one is likely doomed as well since the fungus is still around in the immediate area). The chestnut blight fungus was accidentally introduced to North America around 1900, prior to that time, you could find mature chestnut trees in eastern forests that were over 100 feet high and over 10 feet in diameter at the base! The Mannahatta book talks about majestic chestnut forests once covering parts of Manhattan Island.
This is the tree that produces the chestnuts people eat (or roast over the open fire at Christmas). The nuts are covered with a spiky burr (called the cupule) which protects it from squirrels. The cupule typically falls from the tree around the time of the first frost and split open into four parts releasing the nuts (usually 3) inside. The nuts provide food for squirrels, turkey, deer, black bear, and humans.
The wood of the American chestnut was also valued. It's a straight-grained hardwood rich in tannins which makes it resistant to decay. It's a shame we lost such a majestic tree to a fungal blight.