Arched Sedge (Carex repanda)
The Arched sedge was described in 1894, it is, or maybe, was apparently restricted to the Khasi Hills, a low mountain formation on the Shillong Plateau in Meghalaya, India. [1]
the species appears to be extinct now.
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[1] Joseph Dalton Hooker: The flora of British India. London: L. Reeve 1875-1897
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edited: 21.09.2020
Lovely Sedge (Carex lepida)
The Lovely Sedge is known only from a single population that was recorded more than 100 years ago on the slopes of the Pichincha Volcano in Ecuador.
The species was never found since and is very likely extinct.
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edited: 21.09.2020
Herbst’s Oahu Sedge (Carex wahuensis ssp. herbstii)
The Oahu Sedge (Carex wahuensis C.A. Mey.) (see photo) is endemic to the Hawaiian Islands where it seems to be quite common and widespread.
One of the three recognized subspecies, however, was obviously restricted to a single locality in the Moanalua Valley in the Ko’olau Mountains on O’ahu, Hawaiian Islands and appears to be known by only a single collection.
This form is now considered extinct.
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edited: 21.09.2020