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Dichotomous Key/Ceratozamia

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Ceratozamia
Ceratozamia mexicana
KingdomPlantae
DivisionCycadophyta
ClassCycadopsida
OrderCycadales
FamilyCycadaceae
GenusCeratozamia

Information related to Ceratozamia

Wikipedia • Wikispecies •

Wikicommons
Glossary for this page
(all links are to Wikipedia articles)
Bipinnate: Leaf arrangement where the leaflets of a pinnate leaf are also pinnately divided. Also called "twice pinnate".
Midrib: The central, most prominent vein of a leaf or leaflet.
Pinna(e): Leafy segment of a single pinnate blade, sometimes appearing to be an individual leaf.
Pinnule: Ultimate free leaflet of a multi-pinnate leaf.
Rachis: The main stem of a compound leaf.
Spine: A stiff, sharp structure; usually a modified leaf or stem.
Sporophyll: A modified leaf that bears the plant's spores.

Ceratozamia is a genus of New World cycads in the family Zamiaceae. The genus contains 27 known currently living species and one or two fossil species. Most species are endemic to mountainous areas of Mexico, while few species extend into the mountains of Guatemala, Honduras and Belize.[1][2] The genus name comes from the Greek ceras, meaning horn, which refers to the paired, spreading horny projections on the male and female sporophylls of all species.[3][4]

Many species have extremely limited ranges, and almost all described species are listed as vulnerable, endangered, or critically endangered by the IUCN Red List. The whole genus is listed under CITES Appendix I / EU Annex A, and CITES prohibits international trade in specimens of these species except when the purpose of the import is not commercial, for instance for scientific research. Illegal plant poaching has posed a major threat to Ceratozamia species.[5]

This is the key to the Ceratozamia:

Start

  • 1: Leaflets are the widest above the middle of the frond.
  • 2: Leaflets are the widest below the middle of the frond.

1

Leaflets are the widest above the middle of the frond.

2

Leaflets are the widest below the middle of the frond.

  • 9: Leaflets are less than ten millimeters wide.
  • 10: Leaflets are greater than one centimeter wide.

3

Leaflets are evenly spaced.

  • 4: Leaflets are less than five centimeters wide.
  • 5: Leaflets are more than five centimeters wide.

4

Leaflets are less than five centimeters wide.

  • 6: Leaflets are leathery; stiff and tough, but somewhat flexible.
  • 7: Leaflets are not leathery.

5

Leaflets are more than five centimeters wide.

  • Ceratozamia euryphyllidia: Leaflets are nine centimeters wide or greater, and translucent.
  • 8: Leaflets are less than nine centimeters wide, and not translucent.

6

Leaflets are leathery; stiff and tough, but somewhat flexible.

7

Leaflets are not leathery.

8

Leaflets are less than nine centimeters wide, and thin or papery.

9

Leaflets are less than ten millimeters wide.

10

Leaflets are greater than one centimeter wide.

  • 12: Leaflets are ten to fifteen millimeters wide.
  • 13: Leaflets are two to five centimeters wide.

11

Rachis is not straight.

12

Leaflets are ten to fifteen millimeters wide.

  • 14: Petiole and rachis are green, bearing stiff prickles.
  • Ceratozamia kuesteriana: Petiole and rachis are dark green to brown, lacking stiff prickles.

13

Leaflets are two to five centimeters wide.

  • 15: Leaflets are three centimeters wide or greater.
  • Ceratozamia mexicana: Leaflets are three centimeters wide or less.

14

Petiole and rachis are green, bearing stiff prickles.

15

Leaflets are three centimeters wide or greater.

16

Rachis has stiff prickles or spines.

References

  1. ↑ "World Checklist of Selected Plant Families: Royal Botanic Gardens, Kew". kew.org.
  2. ↑ Hill, K.D. & Stevenson, D.W. (1999). A world list of Cycads, 1999. Excelsa 19: 67-72.
  3. ↑ Standley, P. C. & J. A. Steyermark. 1958. Cycadaceae. In Standley, P.C. & Steyermark, J.A. (Eds), Flora of Guatemala – Part I. Fieldiana, Botany 24(1): 11–20.
  4. ↑ Vovides, A. P., J. D. Rees & M. Vázquez-Torres. 1983. Zamiaceae. Flora de Veracruz 26: 1–31.
  5. ↑ Christenhusz, M. J. M., J. L. Reveal, A. K. Farjon, M. F. Gardner, R. R. Mill & M. W. Chase. 2011. A new classification and linear sequence of extant gymnosperms. Phytotaxa 19: 55–70.
  • Jones, David L. Cycads of the World: Ancient Plants in Today's Landscape. Smithsonian Books: Reed, Sydney, 2002.
  • Walters, T. and Osborne, R. 2004. Cycad Classification Concepts and Recommendations. Wallingford UK: CABI Publishing.
  • Whitelock, Loran. The Cycads. Portland: Timber Press, 2002.
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