''Dendroceros'' is a
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
hornworts in the
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Dendrocerotaceae.
[Renzaglia, Karen S. & Kevin C. Vaughn. (2000) "Anatomy, development and classification of hornworts", pages 1-20 ''in'' A. Jonathan Shaw & Bernard Goffinet (Eds.), ''Bryophyte Biology''. (Cambridge: Cambridge University Press). ] The genus contains about 51 species native to tropical and sub-tropical regions of the world.
Description
The
epiphytic
An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...
and
epiphyllous Dendroceros is the only
desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...
-tolerant hornwort genus.
The
gametophyte
A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the se ...
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
A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...
is erect when mature, growing up to 5 cm tall. Unlike many hornworts, the surface of the ''Dendroceros'' sporophyte lacks
stomata
In botany, a stoma (: stomata, from Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spa ...
, 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
spore
In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...
s 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 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".
References
External links
{{Taxonbar, from=Q1012912
Hornwort genera
Taxa named by Christian Gottfried Daniel Nees von Esenbeck