Diplazium

Diplazium
Diplazium dietrichianum
Scientific classification
Kingdom:	Plantae
Division:	Pteridophyta
Class:	Pteridopsida
Order:	Blechnales
Family:	Athyriaceae
Tribe:	Diplazieae
Subtribe:	Diplaziinae
Genus:	Diplazium Swartz
Species
see text

Diplazium is a genus of the cliff fern family that specifically includes the approximately 400 known species of twinsorus ferns. The Greek root is diplazein meaning double: the indusia in this genus lie on both sides of the vein. These ferns were earlier considered part of either the Athyriaceae, Dryopteridaceae,^[1] Aspleniaceae, or Polypodiaceae families but are often recognized as belonging to their own taxonomic family. The taxonomy of the genus is difficult and poorly-known, and by 2009 has never been the subject of a complete monographic study.^[2] Their distribution is pantropical, with a few species extending into temperate areas.^[1][3]

The rhizome of the Diplazium genus varies from creeping to erect, and is scaly. Its fronds are deciduous or evergreen, are trophopodic^{[nb 1]} and are either monomorphic or weakly dimorphic. The stipe is green, deeply grooved from above, and is either scaly or glabrous. It always has two lunate vascular bundles. The blades are either singular or in sets of two and are entirely pinnate, range from oblong-lanceolate to deltate, and from herbaceous to papery. It has linear basal sori that are paired back-to-back on the same vein. The indusium is linear and persistent, and the sporangia are brownish. The USDA symbol for the species is DISPLA2. Its ITIS Taxonomic Serial Number is 17501.

Some common varieties include Diplazium hymenodes, the peacock fern; Diplazium pycnocarpon, the glade fern or narrow-leaved spleenwort; Diplazium esculentum, the vegetable fern; Diplazium molokaiense, the Molokai twinsorus fern; and Diplazium lonchophyllum, the lance-leaved glade fern.

Taxonomy

The genus Diplazium as defined in 2003 is probably paraphyletic.^[4]

Selected Species

• Diplazium australe
• Diplazium dietrichianum
• Diplazium esculentum
• Diplazium melanochlamys
• Diplazium molokaiense
• Diplazium pycnocarpon
• Diplazium sibiricum

Notes

1. ^ The trophopod is food storage organ described from a number of North American ferns. It consists of the enlarged and modified leaf base filled with starch storage tissue. See W. H. Wagner, Jr. and D. M. Johnson, Taxon, Vol. 32, No. 2 (May, 1983), pp. 268-269 for more information on this organ.

References

1. ^ ^{a b} "3. Diplazium Swartz", Flora of North America, http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=110366 
2. ^ Leticia Pacheco and Robbin C. Moran. Lectotypification of Several Names Currently Placed in Diplazium (Woodsiaceae). American Fern Journal, Vol. 93, No. 2 (Apr. - Jun., 2003), pp. 90-92
3. ^ Diplazium esculentum (Retz.) Sw., GRIN Taxonomy for Plants
4. ^ A. R. Smith, K. M. Pryer, E. Schuettpelz, P. Korall, H. Schneider, P. G. Wolf. 2006. "A classification for extant ferns". Taxon 55(3), 705-731 (pdf here)