I was launching my boat on a ramp into the Hudson River yesterday when I stepped on two seed or seedpods. The seedpod was black in color and had several prickly arms. No matter how you toss the seeds, one of the arms always point upward. The pointy arm was so sharp that it pierced thru my flip flops and cut my feet. What kind of seed was that? I threw it into the water and it floated away.