Answer: Black walnut (Juglans nigra) trees are deciduous, so they have no leaves in winter but you might contact the Morris Arboretum in Chestnut Hill (http://www.upenn.edu/morris/) for assistance in locating a black walnut tree so you can see some first hand in a few months. They might also have a (dried) specimen in their library. The telephone number is 215-247-5777. Here is a photograph of the foliage http://bluehen.ags.udel.edu/udbg/trees/images/cd9_0031.gif and a photograph of a mature tree to look at in the meantime.
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