{{Short description|Species of flowering plant}} {{Use New Zealand English|date=May 2023}} {{Use dmy dates|date=May 2023}} {{Speciesbox | image = Myosotis exarrhena 75636657.jpeg | status = LC | status_system = IUCN3.1 | status_ref = | genus = Myosotis | species = exarrhena | authority = [[F.Muell]]<ref name="Mueller">{{Cite Q|Q51433898}}</ref> | synonyms = ''Exarrhena suaveolens'' [[R.Br.]] }} '''''Myosotis exarrhena''''' is a species of [[flowering plant]] in the [[Family (taxonomy)|family]] [[Boraginaceae]], [[Endemic species|endemic]] to Australia. [[Robert Brown (botanist, born 1773)|Robert Brown]] described this species as ''Exarrhena suaveolens'' in 1810. Plants of this species of [[Forget-me-nots|forget-me-not]] are [[Perennial plant|perennial]] rosettes with ebracteate inflorescences and white corollas with exserted stamens.

== Taxonomy and etymology == ''Myosotis exarrhena'' [[Ferdinand von Mueller|F.Muell.]] is in the plant family [[Boraginaceae]]. The species was originally described by [[Robert Brown (botanist, born 1773)|Robert Brown]] in his ''[[Prodromus Florae Novae Hollandiae et Insulae Van Diemen|Prodromus]]'' in 1810 as ''Exarrhena suaveolens'' R.Br.<ref>{{Cite Q|Q51522645}}</ref> It was transferred to the genus ''Myosotis'' as ''M. suaveolens'' (R.Br.) Poir. in 1816, but this was an illegitimate name owing to ''M. suaveolens'' [[Waldst.]] & [[Kit.]] ex [[Willd.]], which was published in 1809 based on a European type.<ref name=":5">{{Cite Q|Q107670735}}</ref>''<ref name=":6" />'' [[Ferdinand von Mueller]] finally made the valid combination ''M. exarrhena'' in 1889 in the updated ''[[Systematic Census of Australian Plants]].''<ref name="Mueller">{{Cite Q|Q51433898}}</ref>[[File:Myosotis exarrhena.jpg|alt=|thumb|Habit and flowers of Myosotis exarrhena observed in Victoria, Australia]]

The lectotype (K001094009) and the isolectotype (K001094010) of ''Exarrhena'' ''suaveolens'' are on the same sheet at [[Kew Herbarium]],<ref>{{Cite web |title=Lectotype and isolectotype of Myosotis exarrhena on JSTOR |url=https://plants.jstor.org/stable/10.5555/al.ap.specimen.k001094010 |access-date=2023-05-14 |website=plants.jstor.org}}</ref> and were designated by Peter G. Wilson & Jeannie Highet.''<ref name=":6">{{Cite Q|Q118358923}}</ref>''

''Myosotis exarrhena'' is one of two species native to Australia.<ref name=":5" /> ''[[Myosotis australis]]'' is native to Australia, as well as New Zealand and New Guinea''.<ref name=":5" /> Myosotis exarrhena'' is morphologically more similar to other ebracteate-erect species from New Zealand, especially ''Myosotis concinna,''<ref name=":7">{{Cite Q|Q107671092}}</ref> than to ''M. australis.''<ref name=":5" /> The Australian ''M. exarrhena'' can be distinguished from the New Zealand ''M. concinna'' by its white corollas, retrorse hairs on the underside of the rosette leaves and scape, and lack of hooked hairs on the calyx.<ref name=":7" />

The species epithet ''exarrhena'' is based on the Greek word ''arrhen'' and refers to the exerted anthers.<ref name=":5" />

== Phylogeny == One individual of ''Myosotis exarrhena'' was included in [[Phylogenetics|phylogenetic]] analyses of standard DNA sequencing markers ([[Ribosomal DNA|nuclear ribosomal DNA]] and [[chloroplast DNA]] regions).<ref name=":1">{{Cite journal |last1=Meudt |first1=Heidi M. |last2=Prebble |first2=Jessica M. |last3=Lehnebach |first3=Carlos A. |date=2015-05-01 |title=Native New Zealand forget-me-nots (Myosotis, Boraginaceae) comprise a Pleistocene species radiation with very low genetic divergence |url=https://doi.org/10.1007/s00606-014-1166-x |journal=Plant Systematics and Evolution |language=en |volume=301 |issue=5 |pages=1455–1471 |doi=10.1007/s00606-014-1166-x |issn=2199-6881|url-access=subscription }}</ref><ref name=":0">{{Cite Q|Q30707919}}</ref> [[File:Myosotis exarrhena 254945697.jpeg|thumb|Inflorescences with flowers]] Within the southern hemisphere lineage, species relationships were not well resolved.<ref name=":1" /><ref name=":0" /> The individual of ''M. exarrhena'' grouped with Australian ''M. australis'' and several other mostly ebracteate-erect New Zealand ''Myosotis'' species''.<ref name=":1" /><ref name=":0" />''

== Description == '''''Myosotis exarrhena''''' plants are rosettes that are often stoloniferous. The rosette leaves have [[Petiole (botany)|petioles]] that are 6–30&nbsp;mm long. The rosette leaf blades are 7–55&nbsp;mm long by 2–10&nbsp;mm wide (length: width ratio 1.0–7.6: 1), lanceolate, oblanceolate or narrowly oblanceolate, widest below, at or above the middle, usually with an [[Glossary of leaf morphology#obtuse|obtuse]] apex. Both surfaces of the leaf are uniformly and densely covered in flexuous to curved, usually appressed, antrorse (forward-facing) hairs that are oriented parallel to the midrib'''.''' Each rosette has multiple ascending''',''' branched ebracteate [[inflorescence]]s that are bifurcating at the top and up to 470&nbsp;mm long. The cauline leaves are similar to the rosette leaves, but become smaller. The flowers are 36–91 per inflorescence and each is borne on a short [[Pedicel (botany)|pedicel]] without a bract. The calyx is 2–5&nbsp;mm long at flowering and 3–6&nbsp;mm long at fruiting, lobed to half to two-thirds of its length, and densely covered in straight to flexuous, often hooked, patent to erect, mostly antrorse hairs (with some retrorse or backward-facing hairs near the base). The corolla is white and 5–11&nbsp;mm in diameter, with a cylindrical tube, petals that are usually narrowly ovate or ovate, and small yellow scales alternating with the petals. The anthers are fully exserted. The four smooth, shiny, usually medium to dark brown nutlets are 1.7–2.3&nbsp;mm long by 1.0–1.5&nbsp;mm wide and usually ovoid in shape.<ref name=":5" />

The pollen of ''Myosotis exarrhena'' is of the ''exarrhena'' type.<ref name=":5" />

The chromosome number of ''M. exarrhena'' is unknown.<ref name=":5" />

Flowering and fruiting between October–March, with the main flowering period from December–February.<ref name=":5" />

== Distribution and habitat == ''Myosotis exarrhena'' is endemic to Australia in the states of New South Wales, Australian Capital Territory, Victoria and Tasmania from 555 to 1000 m ASL, possibly up to 1370 m ASL, in forest, woodland, clearings or stream banks, on slopes, outcrops or banks.<ref name=":5" />

== Conservation status == ''Myosotis exarrhena'' is not listed on the Australian Government's EPBC Act list of Threatened Flora.<ref>{{Cite web |title=EPBC Act List of Threatened Flora |url=http://www.environment.gov.au/cgi-bin/sprat/public/publicthreatenedlist.pl?wanted=flora#flora_critically_endangered |access-date=15 May 2023 |website=Species Profile and Threats Database}}</ref> It is likely to be considered to be LC (Least Concern) according to the IUCN.<ref name=":5" />

== Hybridisation == On the basis of morphological data, ''Myosotis exarrhena'' may hybridise with ''M. australis'' where the two species are known to co-occur in New South Wales, ACT and Victoria.<ref name=":5" /> Several specimens have been identified as interspecific ''M. exarrhena'' × ''M. australis'' hybrids.<ref name=":5" />

== References == {{Reflist}}

== External links == {{Commons}} * [https://avh.ala.org.au/occurrences/search?taxa=myosotis+exarrhena#tab_mapView ''Myosotis exarrhena'' occurrence data from Australasian Virtual Herbarium]

{{Taxonbar|from=Q17416562}}

[[Category:Myosotis|exarrhena]] [[Category:Endemic flora of Australia]] [[Category:Taxa named by Robert Brown (botanist, born 1773)]] [[Category:Plants described in 1810]]