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| | Math Trek: The Mathematical Lives of Plants, Science News Online, May 5, 2007 (Site not responding. Last check: 2007-10-26) |
 | | The seeds of a flower head form interlocking spirals in both clockwise and counterclockwise directions. |
 | | The number of clockwise spirals differs from the number of counterclockwise spirals, and these two numbers are called the plant's parastichy numbers (pronounced pi-RAS-tik-ee or PEHR-us-tik-ee). |
 | | Buds 0, 13, and 26 form a clockwise spiral and buds 0, 8, 16, 24, and 32 form a counterclockwise spiral. |
| www.sciencenews.org /articles/20070505/mathtrek.asp (1465 words) |
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