Dendroceros
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Through Gametophyte, Stoma and Spore
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 (usually Nostoc) 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.
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Classification
Current classification by Söderström et al. 2016.
Genus Dendroceros Nees 1846
- D. australis Stephani 1909
- D. crassicostatus Stephani 1917
- D. exalatus Stephani 1909c
- D. gracilis Stephani 1917b
- D. humboldtensis Hürlimann 1960
- D. rarus Stephani 1917b
- D. reticulus Herzog 1950b
- D. subtropicus Wild 1893
- D. tahitensis Ångström 1873
- D. vesconianus Gottsche ex Bescherelle 1898
- D. wattsianus Stephani 1909
- Subgenus (Cichoraceus) Peñaloza-Bojacá & Maciel-Silva 2019
- D. cichoraceus (Montagne 1845) Stephani 1916
- Subgenus (Dendroceros) Nees 1846
- D. acutilobus Stephani 1909
- D. adglutinatus (Hooker & Taylor 1845) Gottsche, Lindenberg & Nees 1846
- D. allionii Stephani 1917
- D. breutelii Nees 1846
- D. crassinervis (Nees 1846) Stephani 1917
- D. crispus (Swartz 1788) Nees 1846
- D. foliicola Hasegawa 1980
- D. herasii Infante 2010
- D. javanicus (Nees 1830) Nees 1846
- D. paivae Garcia, Sérgio & Villarreal 2012
- D. rigidus Stephani 1917
- D. subplanus Stephani 1909
- D. tubercularis Hattori 1944
- D. validus Stephani 1917
- Subgenus (Nodulosus) Peñaloza-Bojacá & Maciel-Silva 2019
- D. africanus Stephani 1917
- D. borbonicus Stephani 1892
- D. crispatus (Hooker 1830) Nees 1917
- D. granulatus Mitten 1871
- D. japonicus Stephani 1909
- Subgenus (Apoceros) 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".