Phylogeny
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Anthocerophyta: Hornworts

Viridiophytes: green plants -> Embryophytes: Land plants

The hornworts comprise a relatively small monophyletic group of about 100-150 species in 12 named genera. They are characterized by life history, growth form, chloroplast structure and numbers, antheridia number and jacket cell organization, Nostoc colony organization, presence of mucilage canals, and thallus outgrowths. The development of histogenic regions, spore and pseudoelater architecture and ultrastructure and the presence of columella and stomata are diagnostic features of the sporophyte. An intriguing feature of hornworts is the large solitary chloroplast with a prominent pyrenoid. This is shared with some green algae, but is not found in any other land plants. However pyrenoids have been lost multiple times within hornworts and similar losses and gains have been described in several algal lineages. A second feature is the presence of stomates. Stomata are specialized structures that facilitate gas exchange. The evolution of stomata is one of the most significant innovations that spurred the diversification of land plants. Their presence in hornworts may be homologous to similar structures found in mosses and vascular plants. Alternately stomata may have evolved independently in these groups.

Indigenous or exotic to New Zealand.

NZ Flora Web Site Link to the Ngā Tipu o Aotearoa Database

 
References
Cargill, D. C.; Renzaglia, K. S.; Villarreal, J. C.; Duff, R. J. 2005: Generic concepts within hornworts: historical review, contemporary insights and future directions. Australian Systematic Botany 18: 7-16.
Shaw, J.; Renzaglia, K. 2004: Phylogeny and diversification of bryophytes. American Journal of Botany 91: 1157-1581.
Last updated: 05-Mar-2013