Dichotomous Key

A.Plant with Needles. – Plant 1.

A1. Plants with leaves. – B

B. Plant with complete flowers. – C

B1. Plant with incomplete flowers, only staminates and pistillates – Plant 4

C.Plant with white petals – Plant 2

C1.  Plant with purple petals – Plant 3


  1. Emma Snodgrass


    I like the flow of your key. It is clear to me what sections are intended to go where, especially with the “– Letter” at the end.

    Having said that, wouldn’t needles still fall under the leaves? To avoid such confusion, you may want to try a different differentiation. Maybe leaf shape?

    A thought: I wonder if the “leaves” (light green, “frilly”/pubescent) on plant 3 might actually be sepals? If this is the case, then I am not sure where the leaves are/what they look like (if this plant has any), making it possibly problematic for this key (due to it being based on the presence of leaves). However, I could be totally wrong about this. It is hard for me to tell from the photos.

    I do like the use of complete vs. incomplete. However, it was difficult for me to tell definitively if plant 2 was complete. It looks like you can see anthers but I couldn’t see any stigma or styles indicative of a pistil. Could you explain how you concluded it was complete?

    Emma S.

  2. Thanks Emma,
    plant 3 is an example of the pasqueflower http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500080, I did not give you all the information from this plant, but knowing that really all reproductive parts of a flower are modified leaves, one can recognize green pubescent ‘leaves’ on the peduncle, these are involucral bracts (which are indeed modified leaves, you would find stomata on these structures, and as such they have all the characteristics of a leaf). The ‘true’ leaves in pasqueflower are basal (see below from FNA), and I did not include an image of those. I think the way Dorene was using needles vs. leaves is the traditional way, we talk about flowering seed plants (angiosperms) and naked seed plants (gymnosperms), the former most often having leaves, sometimes they can be reduced to being needle-like, but needles are most commonly associated with gymnosperms (although there are some that have blade-like needles (Ginkgo, some podocarps, cycads, and others). For sure the plant 1 (spruce) example would be classified as having needles. As far as the flowers in 2 and 3 being complete, this would be an assumption based on what Dorene might think these plants are (in the Brassicaceae, and Ranunculaceae respectively, which commonly have complete flowers with some exceptions). It was indeed not obvious from the pictures. Thanks!

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