All of us do know that plants evolved from green algae, but the algae is from fresh water or oceans?
It is most likely a freshwater algae.
I believe it is closely related to the Stonewort which is freshwater.
my last palaeobotany lessons were more than a decade ago, so I had a look at my literature here (end 80s), which says that Bryophytes and Tracheophytes (mosses and vascular plants) are either monophyletic or polyphyletic and most closely related to either Ulotrichales or Chaetophorales or Charales and either of freshwater or of marine origin. *lol*
A 2003 paper on http://eprints.whiterose.ac.uk/106/1/wellmanch1.pdf" says Bryophytes and Tracheophytes are most likely monophyletic and sister to Charales. Furthermore the sediments the first tiny plant fragments were found in "suggest a marginal marine setting, a predominantly non-marine environment with minor marine incursions, or an entirely non-marine sequence into which the rare marine elements are reworked." *smile*
While fossil evidence isn't clear about freshwater or marine origin of land plants, wikipedia (citing the 2003 paper) asserts a freshwater origin ... I thing this conclusion comes from the sistergroup relationship to Charales. As extant species of http://en.wikipedia.org/wiki/Charales" [Broken] are growing in brackish or freshwater environments.
Some good fossils of early land plants, when being found, might confirm or change that view.
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