Monday, April 27, 2009

Keying Out a Mustard Part 2

This has been sitting in the stack for several weeks now, just waiting for a little editing. Now that my hands are starting to recover from carpal tunnel syndrome, I am finally getting it out the door.

In the first part of this series I started down the wrong branch of the key from the very first step. Now that I have the initial problem straightened out, let's see where we can get to. (Thanks again Kitty for the comments in italics.)

(Again I am using Hitchcock and Cronquist's Flora of the Pacific Northwest if you would like to follow along)

With the sessile fruit (1b), the next choice is (5b): pod uniform, not divided crosswise into 2 segments (this threw a bit as I wasn't certain at first which direction they meant by crosswise, but the illustration made it clear enough).

I find the illustrations in the key very useful, probably more useful than the glossary.

The next choice was even easier: the fruit is a silique (long and thin) rather than a silicle (closer to round) (6b).

Petals are white (12b).

It would be easy to get caught up in the difficult terminology in the next choice (and I did go through it when keying out initially), but we can simply note that our plant does not fit into the more easily understood criteria (e.g. petals are not 11-15 mm) so we make our choice (13b).

The petal size is probably the most straightforward of the criteria, but the description included in the couplet "grayish with branched hairs; petals...pinkish to purple" and the habitat were also good clues that 13b was the correct choice.

The next split is on whether the seeds are uniseriate or biseriate (a single series or a double series). This was a little confusing to me because the fruit has a series of seeds on each side - so there are two series of seeds, but each series is in a single line. The illustrated glossary that I use pictured biseriate as being two series in the same enclosure (e.g. a row of seeds attached to the top of the enclosure alternating with a row of seeds attached to the bottom - like a zipper). Based on that interpretation (that the fruit contained two sets of uniseriate seeds) I jumped to group VII.

The comparison to a zipper seems particularly useful.

The next choice (74b) was easy to make based on size of the petals and seeds, but I would like to point out the word torulose (just for fun).

I kind of like connivent: converging or coming together, but not organically united.

This is a good spot to point out that sometimes it is easy to choose a couplet based on familiarity with a genus. More simply put, if you know it isn't a Hesperis, take the other lead. This doesn't always work though...

Siliques of this plant are dehiscent (75b) - another common name for the plant (probably the genus in general) is shotweed: when the plant dries, the little panels holding the seeds in will often spring back at a touch, shooting the seeds out like shot.

So if you don't know that the fruit are dehiscent; it might be wise to look at the two genera included under 75b. We can eliminate Raphanus because the fruit are not torulose. Streptanthella can be eliminated by the leaves (the drawing included with the genus was helpful, as was the description)

Leaves are definitely not entire (77b).

This one's a bit tricky: Pubescence (hair) simple or branched? With the size of the hairs on these plants this probably needs some magnification. With a fresh sample I might have been able to eyeball it, but a hand lens would definitely be in order. My microscope was handier today, and all the hairs I could see on my dried out sample were simple (78a).

The hairs visible in the photo were not branched. The photo was quite useful for identification.

Siliques much less than 5cm (79b).

I focused on the calyx not being urn-shaped and the features of the petal

Stem leaves all pinnate (81a), (82b) which takes us to the genus Cardamine.

I will leave determination of the species to the final part of this series.

The species determination should be interesting.

first part of the series

No comments: