Tuesday, March 10, 2009

Plant Identification Class

Microsope at a Workbench in Hitchcock - UW
This evening I started a six week course (one night a week) on plant identification. The course is offered by the University of Washington Botanical Gardens. From the course description: “This course is designed for individuals who want to work on field identification skills and gain familiarity with how to use the keys in Hitchcock and Cronquist's Flora of the Pacific Northwest. Sounded pretty interesting, so here I am.

So what is plant identification? Well, it involves using an identification key. To describe an identification key I’ll quote Botanical Primer by Joseph Arnett (2005) passed out in class:

Identification keys are the primary tools used to identify unknown plants, and most botanical keys are dichotomous. A dichotomous key is constructed of sets of paired questions, or couplets, that are like a series of forks in the road. At each fork the user has to make a choice, based on the two descriptions that are offered, and go one way or the other. Each choice leads to a set of questions until, eventually, the identity of the unknown species is reached. One great value of dichotomous keys is that they identify the particular characteristics that may be used to distinguish species or groups of species. These diagnostic traits may not always be apparent in illustrations or descriptions.

So we will be working through keys to identify plants. But first, before we can do that we need to have a grasp on some of the botanical nomenclature used in the keys. This is what most of the first class was about. To illustrate points, different plant specimens were passed out. Quite frankly it’s an alphabet soup of very interesting words like calyx, corolla, pistil, stamen, actinomorphic, zygomorphic, petioles, verticil, lenticel, and axil just to name a couple of the ones I remember off the top of my head. (Answers at the end.)

To aid in dealing with the nomenclature we had a couple of handouts that were good and a recommendation for the book Plant Identification Terminology: An Illustrated Glossary by Harris and Harris. I picked this book up and am pleased with it so far.
Plant Identification Terminology
Answers: Calyx refers to the sepals of a flower. Corolla refers to the petals of a flower. Pistil refers to the female reproductive organ of a flower. Stamen refers to the male reproductive organ of a flower. Actinomorphic refers to a flower that is radially symmetric. Zygomorphic refers to a flower that is bilaterally symmetric. Petioles refer to the leaf stalk that attaches a leaf to a stem. Verticil refers to an arrangement of similar parts (like flowers) around a central axis (like a stem). Lenticels are specialized corky outgrowths from the bark of twigs that are passageways for gas exchange. Axil refers to the space between the petiole and stem.

There is a diagram (redrawn and modified below) from Arnett’s primer that was especially helpful for orienting myself to what we are to study in this class: vascular plants.
Kingdom Plantae

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