I believe this is the seeed of the black mangrove tree. I saw them all over the beach last week too, only now they are sprouting. Since I am mobile, I cannot look it up easily at the moment but I will when I get home and add a comment to this post to confirm. Dang, I should carry a field guide…
I can confirm that this is the seed of a black mangrove tree. I knew I’d seen it somewhere – turns out it was on the blog for the Sanibel Sea School. Check it out!
http://sanibelseaschool.org/blog/2011/09/07/what-is-that-bean-on-the-beach/
Before I read your text I though, oh, a green cherry with a fuzzy stem! I am SO not a naturalist, LOL.
I didn’t realize it was sprouting, at first – I thought some sort of critter had taken up residence inside!
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We’re so glad the blog helped you out! Let us know what other intriguing things you are finding on the beaches, our curious minds are always up for a challenge!