Pier’s Dichotomous Key

Making a dichotomous key was really tough. I struggled with understanding the morphology of the plants across different species in order to be able to identify similarities. For example- are the leaves on the purple plant the sepal? Seems like it should be except it looks like they could also be leaves in a whorl that the stem rises out of. The leaves on plant 4 seem to be whorls- but can’t see it clearly. So I made a list of descriptions for each plant and then created the dichotomous key. It took a really long time actually b/c I had to research the words to be able to describe/identify it.

Plant 1 Description
Green coniferous needles
White line on underside of needle
Somewhat pointed needle tips
Grows around entire radius of branch
Scaled brown pine cones
Bud at tip
Whorled Branches

Plant 2 Description
Inflorescence tiny white flowers
Flowers have green sepals with little hairs on them
4 petals
Yellow Stamen? Yellow Anthers? Or pistils- hard to see. Center.
Green stems have hair on them
leaves so skinny look like needles but soft
Alternate positioning on stem

Plant 3 Description
Hair on green stems
Purple petals
White stigma
Yellow Stamen? Yellow Anthers?
Leaves positioned in whorls
Leaves green and skinny and needle shaped but soft
Leaves have hairs on them

Plant 4 description
Yellow and red anthers
Green leaves with fine hairs on them
Leaves positioned in whorls
Conular

Dichotomous Key
Flowers:
Flowers with white petals………….Plant 2
Flowers with purple petals…………Plant 3
Flowers with yellow anthers.…….. Plant 2, Plant 3, Plant 4
Deciduous Flowers/Stems/Leaves………………….………. Plant 2, Plant 3, Plant 4
Coniferous Flowers/Branches/Needles…………….……… TBD Plant 1
Deciduous Stems/Leaves:
Green skinny leaves…………………….…..Plant 2, Plant 3
Oblong green leaves…………………………Plant 4
Leaves with hairs……………………..…….Plant 2, Plant 3
Stems with hairs……………………………..Plant 3
Alternate positioning…………………………Plant 2
Whorls……………………………….…… Plant 3, Plant 4 (hard to see all of it)
Coniferous Branches/Stems
Green coniferous needles………………….Plant 1
White line on underside of needle… ……..Plant 1
Somewhat pointed needle tips…………….Plant 1
Grows around entire radius of branch……..Plant 1
Scaled brown pine cones…………………..Plant 1
Bud at tip…………………………………. Plant 1
Whorled Branches………………………….Plant 1

4 Comments

  1. Thanks Pier,
    you did all the hard work describing the plants, the only thing that you would want to modify is streamlining your dichotomous key. Remember the couplets are forks in the road where you can proceed in one of two roads. One road ends with the plant choice – for example plants with needles lacking flowers (plant 1), and the other road plants leaves and flowers contains more than 1 plant (plants 2-4). Thus if we go down this road we will end up at another fork in the road, this time we are faced with a choice of flowers in an inflorescence either with white petals or lacking petals [apetalous] (plant 2 and 4) vs. flowers solitary with purple petals (plant 3). So we leave the road that ends behind (a single plant) and go down the road that has another fork and find a character that allows us to separate the two remaining plants (plant 2 and 4). Plant 2 has white petals and hairs that are forked, while plant 4 lacks petals (it is a willow) and the hairs on the leaves are simple (not forked). The was an exercise to help you understand that writing a key is kind of an art in itself, and there are many solutions to this puzzle, and the more plants you have to accommodate the better you have to be at making these two way choices. Putting things into categories, like sorting legos by color, shape etc. is something humans have done for generations, and we are really good at it to determine if something is dangerous or poisonous, often marked by bright red colors of the fruits of certain plants.

  2. Olivia

    Dichotomous Key Updated*
    For this assignment, I read your dichotomous key, Prof. Ickert-Bond’s response, and then used your key to identify the plant examples provided. You determined a lot more attributes and definitions than I did in the process of creating our keys. Good work! Your formatting is neat. I relearned “whorl” through your post. One term that I encountered that might work here, strigose indicates the existence of hairs. Glabrous/ puberulent describe hairless plant parts.
    My only criticism would be the either/or aspect of the dichotomous key. The statement you make to categorize your plants should only have 2 options. It helped me to think about coming across a path with 2 direction options, the eye doctor choosing between lenses, or the choose your own adventure stories from my childhood. Anyways, I combined out Dichotomous Keys to create a much better key. Thanks!
    To post the document, I will have to create a new post. It’s much prettier on word. Check it out.

  3. Aihs Palmer

    Hi Pier,

    I agree that making the key was tough but it was due to my own overthinking. I think that when it comes to school work we are so used to things being complex and especially in the sciences leaving information out can be make you lose a lot of your work. In a course like this you you feel compelled to write down every detail. Your key looks a lot like how mine did before I asked the instructor for some clarification. I had every characteristic written down. All that you need to do is simplify your key but its a great example of how we process this activity before we are comfortable with the material.

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