Dendroceros


Dendroceros is a genus of hornworts in the family Dendrocerotaceae. The genus contains about 51 species native to tropical and sub-tropical regions of the world.

Description

The epiphytic and epiphyllous Dendroceros is the only desiccation-tolerant hornwort genus. The gametophyte is yellowish-green and usually less than one-half cm wide. The thallus branches in a bifurcating pattern. In the subgenus Apoceros, there are cavities in the central strand of the thallus. The edges of the thallus are only a single layer of cells thick and have an undulating margin. It is common to find symbiotic colonies of blue-green bacteria growing among the cells. Under a microscope, the epidermal cells have trigones.
The sporophyte is erect when mature, growing up to 5 cm tall. Unlike many hornworts, the surface of the Dendroceros sporophyte lacks stomata, as do the sporophytes of the related genera Megaceros and Nothoceros. The interior of the sporophyte differentiates into a central column and a surrounding mass of spores and elater cells, with a distinct spiral. The spores are green and multicellular with an ornamented surface.

Classification

Current classification by Söderström et al. 2016.
Genus Dendroceros Nees 1846D. australis Stephani 1909D. crassicostatus Stephani 1917D. exalatus Stephani 1909cD. gracilis Stephani 1917bD. humboldtensis Hürlimann 1960D. rarus Stephani 1917bD. reticulus Herzog 1950bD. subtropicus Wild 1893D. tahitensis Ångström 1873D. vesconianus Gottsche ex Bescherelle 1898D. wattsianus Stephani 1909Subgenus Peñaloza-Bojacá & Maciel-Silva 2019
  • * D. cichoraceus Stephani 1916Subgenus Nees 1846
  • * D. acutilobus Stephani 1909
  • * D. adglutinatus Gottsche, Lindenberg & Nees 1846
  • * D. allionii Stephani 1917
  • * D. breutelii Nees 1846
  • * D. crassinervis Stephani 1917
  • * D. crispus Nees 1846
  • * D. foliicola Hasegawa 1980
  • * D. herasii Infante 2010
  • * D. javanicus Nees 1846
  • * D. paivae Garcia, Sérgio & Villarreal 2012
  • * D. rigidus Stephani 1917
  • * D. subplanus Stephani 1909
  • * D. tubercularis Hattori 1944
  • * D. validus Stephani 1917Subgenus Peñaloza-Bojacá & Maciel-Silva 2019
  • * D. africanus Stephani 1917
  • * D. borbonicus Stephani 1892
  • * D. crispatus Nees 1917
  • * D. granulatus Mitten 1871
  • * D. japonicus Stephani 1909Subgenus Schuster 1987b
  • * D. cavernosus Hasegawa 1980
  • * D. cucullatus Stephani 1923
  • * D. difficilis Stephani 1917
  • * D. muelleri Stephani 1889
  • * D. ogeramnangus Piippo 1993
  • * D. pedunculatus Stephani 1909
  • * D. seramensis Hasegawa 1986
  • * D. subdifficilis Hattori 1951

Habitat

Dendroceros grows on humid ground, rocky outcrops, and on the sides of trees. Its name literally means "tree horn".