Hi, peduncle 1 : a stalk bearing a flower or flower cluster or a fructification [M-W's Dictionary] In the above definition flower cluster is one of those compound nouns where I would have used 's to form a compound noun. I believe it is due to the fact that in my native tongue compound nouns are not made just by combining two different words. If I had to do the word for word translation of my native phrase used for flower cluster , then I would have written cluster of flowers or flowers' cluster .
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