from The Century Dictionary.

  • Those petals in a papilionaceous flower which unite to form the keel.


Sorry, no etymologies found.


  • But I have forgotten to say that my maximum difficulty is trees having papilionaceous flowers: some of them, I know, have their keel-petals expanded when ready for fertilisation; but Bentham does not believe that this is general: nevertheless, on principle of nature not lying, I suspect that this will turn out so, or that they are eminently sought by bees dusted with pollen.

    More Letters of Charles Darwin — Volume 2

  • Yet I have seen humble-bees whilst sucking the nectar depress the keel-petals, and become so thickly dusted with pollen, that some could hardly fail to be left on the stigma of the next flower which was visited.

    The Variation of Animals and Plants Under Domestication, Vol. I.


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