Portraits of Wildflowers

Perspectives on Nature Photography

Archive for January 4th, 2013

Why a four-nerve daisy is called a four-nerve daisy

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Click for greater clarity.

Click for greater clarity.

In a comment yesterday Joan Leacott asked why the little yellow daisy with the scientific name Tetraneuris scaposa is called a four-nerve daisy. Today’s photograph, taken like the previous one in northwest Austin on January 2 of 2012, will answer that question.

If you look at the center of the picture you’ll see that every ray is indented into three “teeth” at its tip. Each of those three teeth has two converging brown “nerves” on it. If you were to take a cross-section through those teeth you’d count six nerves. But the teeth aren’t representative of the ray as a whole, and you’ll find that each pair of nerves that flanks an indentation at the tip has grown out of a single nerve lower down on the ray. In other words, if you were to take a cross-section of a ray anywhere other than at the indentations, you’d count four nerves. Voilà, Q.E.D., case closed.

If yesterday’s photograph showed an opening bud of this species, today’s shows a more advanced stage in that opening, when the rays are better developed and already point as much outward as upward.

For more information, and to see a state-clickable map of the places in the south-central United States where Tetraneuris scaposa grows, you can visit the USDA website.

If you’re interested in photography as a craft, you’ll find that points 1, 10, 16, 19 and 23 in About My Techniques are relevant to this photograph.

© 2013 Steven Schwartzman

Written by Steve Schwartzman

January 4, 2013 at 6:17 AM

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