Dichotomous Key Exercise

Creating this key was harder than I thought it would be since I had to resist the urge to make it more complex than it really was. Also, I really wanted to try to describe the leaves but there were not enough (or too many?) dichotomies that I could see from the images.

A. Plant has needle-like leaves – Plant 1
A. Plant has flat or diverse leaves – Plants 2, 3 & 4
– B. Flowers monoecious – Plant 4
– B. Flowers bisexual – Plants 2 & 3
– – C. Petals white – Plant 2
– – C. Petals purple – Plant 3

I sure do hope that there are multiple correct answers for this exercise – fun!

I’m guessing that the purple flower is Pulsatilla patens L. ?
I didn’t know how to describe the leaf so I decided to dissect Hultén’s description to help me understand what to look for.

This is what Hultén say about Pulsatilla patens L. followed by the botanical terms defined.

“Silky-villous; silky-bearing long soft (not interwoven) hairs
stems from vertical, dark-brown, many headed caudex; woody, perennial base of an otherwise herbaceous stem
basal leaves developing after floration, ternately divided into three segments, the divisions 2- or 3- partner into numerous narrow segments;
the very villous involucrum whorl of bracts subtending a flower cluster, deeply cleft into narrow, lanceolate, acute lobes;
sepals blue or purple;
staminodia sterile stamens, or any other structure without anther corresponding to a stamen gland like;
fruit plumose having fine hairs on each side; feathery when ripe.”
~Hultén, Flora of Alaska p. 466

There is no mention of petals in the description above that I can see – why is that?

Dichotomous Key Identification Exercise:
I would like confirmation that the Purple violet in the images is V. nephrophylla and that the White violet is V. renifolia var. brainerdii.
I feel pretty confident that the Spruces shown are 1. Picea glauca and 2. Picea mariana.

3 Comments

  1. Thanks Oona,
    well done on the key. Yes, it is Pulsatilla patens as per Hultén, the correct name is recognized as Pulsatilla nuttaliana see http://www.phytoneuron.net/2016Phytoneuron/79PhytoN-Anemonastrum.pdf. For the violets I have Viola epipsila ssp. repens for the purple one and Viola renifolia for the white one. I had mentioned that both lack a well-developed rootstock in the text. It is also interesting that the two keys are constructed slightly differently. Just as your classmates have created slightly different keys for the exercise, everybody is drawn to a slightly different feature and organizes the key that way.

  2. Sara Cramb

    Excellent work on this Oona! I like how you’ve organized them by leaf type and then further narrowed them down by sex attributes. One additional way to break it down could be the presence or absence of petals right before C.

  3. Jennifer

    You have done a thorough exploration here, Oona! I appreciate reading how you tracked down and evaluated further information about these particular plants. I am often still learning which questions to ask or which choices to examine (let alone getting to the point of actually being able to answer the questions or explain the choices), so it’s always helpful to see how someone got to that point.

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