Dioon

Dioon
Dioon edule
Scientific classification
Kingdom:	Plantae
Division:	Cycadophyta
Class:	Cycadopsida
Order:	Cycadales
Family:	Zamiaceae
Subfamily:	Encephalartoideae
Tribe:	Diooeae
Genus:	Dioon Lindl.[1][2]
Type species
Dioon edule[1] Lindl.
Species
See text

Dioon is a genus of cycads in the family Zamiaceae. It contains 11 accepted species that are native to Mexico, Honduras, and Nicaragua. Their habitats include tropical forests, pine-oak forest, and dry hillsides, canyons and coastal dunes.

Dioons are dioecious, palmlike shrubs with cylindrical stems, usually with many leaves. Leaf bases are persistent or shedding to leave smooth bark. The genus is commonly divided into two groups of distinct morphology. The first includes D. mejiae, D. rzedowskii, and D. spinulosum, which are characterized by the greater size of their fronds, trunks, and cones. The second group contains D. califanoi, D. caputoi, D. edule, D. holmgrenii, D. merolae, D. purpusii, D. sonorense, and D. tomasellii, which are smaller overall, with shorter trunks, much shorter fronds, and smaller cones.^[3]

The leaves are pinnate, spirally arranged, interspersed with cataphylls, with leaflets not articulated and lacking a midrib. The lower leaflets are often reduced to spines. The sporophylls are not in vertical rows in cones, and the megasporophyll apices are broadly flattened, upturned, and overlapping.

Accepted species

• Dioon califanoi De Luca & Sabato
• Dioon caputoi De Luca et al.
• Dioon edule Lindl.
• Dioon holmgrenii De Luca et al.
• Dioon mejiae Standl. & L.O.Williams
• Dioon merolae De Luca et al.
• Dioon purpusii Rose
• Dioon rzedowskii De Luca et al.
• Dioon sonorense (De Luca et al.) Chemnick et al.
• Dioon spinulosum Dyer
• Dioon tomasellii De Luca et al.

List source : ^[4]

References

1. ^ ^{a b} In: Edwards's Botanical Register 29: misc. 59-60. 1843. "Name - Dioon Lindl.". Tropicos. Saint Louis, Missouri: Missouri Botanical Garden. http://www.tropicos.org/Name/40031830. Retrieved February 15, 2010. "Annotation: as 'Dion' ; orth. & nom. cons.
   Type Specimen: Dioon edule Lindl." 
2. ^ Original Publication GRIN (October 5, 2007). "Dioon information from NPGS/GRIN". Taxonomy for Plants. National Germplasm Resources Laboratory, Beltsville, Maryland: USDA, ARS, National Genetic Resources Program. http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?3756. Retrieved February 15, 2010. "Comments: this spelling conserved (nom. cons.)(Vienna ICBN Art. 14.11 & App. III) against the original spelling 'Dion' " 
3. ^ Norstog, K.J. & Nichols, T.J. (1997). The biology of the cycads. Cornell University Press. 
4. ^ GRIN. "Complete List of Accepted Species Records for genus Dioon". Taxonomy for Plants. National Germplasm Resources Laboratory, Beltsville, Maryland: USDA, ARS, National Genetic Resources Program. http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?3756. Retrieved February 15, 2010. 

External links

• Gymnosperm Database: Dioon