Limnobium Richard
(incl. Hydromystria G. Mey.)
Limnobium is, as currently understood (Haynes 2000, Mabberley 2008), a genus of one or two closely related species (L. laevigatum and L. spongia (Bosc) Richard ex Steudel). The former is widely cultivated as an aquatic ornamental or as an aquarium plant. In warm-temperate and (sub-) tropical areas it may behave as a noxious aquatic weed.
Limnobium is obviously closely related to Hydrocharis; both represent the most primitive elements within Hydrocharitaceae (Les & al. 2006). Non-flowering plants of some representatives of the latter are hardly distinguishable from Limnobium. However, both genera are readily told apart on floral characters. In Europe only female plants of Limnobium seem to have been introduced (Mabberley 2008) and plants are very reluctant to flower in our area. Some authors (Díaz-Miranda & al. 1981) maintain Limnobium and Hydromystria as distinct genera based on morphological evidence but this is not supported by molecular data (Les & al. 2006, Chen & al. 2012). If both were accepted, then the only species here concerned should be referred to as Hydromystria laevigata.
Literature:
Catling P.M. & Dore W.G. (1982) Status and identification of Hydrocharis morsus-ranae and Limnobium spongia (Hydrocharitaceae) in northeastern North America. Rhodora 84(840): 523-545.
Chen L.-Y., Chen J.-M., Gituru R.W. & Wang Q.-F. (2012) Generic phylogeny, historical biogeography and character evolution of the cosmopolitan aquatic plant family Hydrocharitaceae. BMC Evolutionary Biology 12: 30 [available online at: http://www.biomedcentral.com/content/pdf/1471-2148-12-30.pdf]
Cook C.D.K. & Urmi-König K. (1983) A revision of the genus Limnobium including Hydromystria (hydrocharitaceae) Aquatic Botany 17(1):1-27.
Díaz-Miranda D., Philcox D. & Denny P. (1981) Taxonomic clarification of Limnobium Rich. and Hydromystria G. W. F. Meyer (Hydrocharitaceae). Bot. J. Linn. Soc. 83(4):311 - 323.
Haynes R.R. (2000) Hydrocharitaceae. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 22. Oxford University Press, New York-Oxford: 26-38. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10426]
Les D.H., Moody M.L. & Soros C.L. (2006) A reappraisal of phylogenetic relationships in the monocotyledon family Hydrocharitaceae (Alismatidae). Aliso 22: 211-230. [available online at: http://www.eeb.uconn.edu/people/les/Manuscript_Files/Aliso_22.pdf]
Lowden R.M. (1992) Floral variation and taxonomy of Limnobium L.C. Richard (Hydrocharitaceae). Rhodora 94(878): 111-134.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.