I cannot tell if plant 3 has a single set of opposite (palmate?) leaves or a whorl. At any rate, the leaf arrangement with a single flower on each stem stands out to me.


  1. Thanks Justin,
    a very minimalistic key, but it gets the job done. Botanists tend to avoid using “no” and “yes” as a description of a couplet. So you could have used: A. Coniferous trees with needles … plant 1 and A’. Trees, shrubs or annuals with various leaf shapes….. B.
    B. Single terminal flower with purple petals on stem ……. plant 3
    B’. Multiple flowers with white petals (or apealous) variously arranged into an inflorescence…. C.
    And then under C. you could use the unisexual flowers arranged in a catkin (plant 4) vs. perfect flowers in a raceme for C’ (plant 2). Generally speaking dichotomous keys tend to use more than one character per couplet, but for this exercise one character is fine. Well done.

  2. Oona Martin

    Justin – In this exercise, I also found plant 3 to have prominent characteristics like the fancy leaf whorl. Since I couldn’t think of a dichotomy to pair with the leaf arrangement that didn’t already exclude the other plants, I didn’t get to use it. It was hard leaving out an observation since I really wanted to talk about it!

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