This is a plant found growing in S. Indiana in a wooded area. It is roughly knee high, twiggy in appearance, in small clumps of 3-4 twigs each, clumps are not very close to each other (closest ones are roughly 10' apart). Soil is average moisture, some clay. I have not seen them in leaf or any blooms. I am guessing the squares are berries; I cut one open and found finely granulated dust inside. The squares are only about a centimeter or two in size but that is a very rough guess as I am horrible at eyeballing measurements!
Did a simple google search 'square seed pod Indiana'
That looks like a Ludwigia alternifolia "seedbox."