Isoetes toximontana

{{short description|South African species of quillwort}}

{{Speciesbox

| name = Gifberg quillwort

| image =

| status = LC

| status_system = IUCN3.1

| status_ref = {{cite iucn |last1=Roux |first1=J.P. |last2=Raimondo |first2=D. |year=2010 |title=Isoetes toximontana |volume=2010 |page=e.T185367A8397474 |doi=10.2305/IUCN.UK.2010-3.RLTS.T185367A8397474.en |access-date=26 May 2024}}

| genus = Isoetes

| species = toximontana

| authority = Musselman & J.P. Roux

}}

Isoetes toximontana, the Gifberg quillwort, is a plant species native to the Northern Cape and Western Cape regions of South Africa. It is known from only 3 sites. The type locality is on the slopes of [http://samountainpasses.co.za/Home/WesternCape/Passes/WESTCOAST/GifbergPass/tabid/257/Default.aspx Gifberg], a mountain forming part of the eastern boundary of the Olifants River Valley. The name "Gifberg" means "poison mountain"; this is in reference to a poisonous tree called "gifboom", Euphorbia virosa, that is endemic to the area. The specific epithet "toximontana" is a Latin translation of the Afrikaans name of the mountain.[http://samountainpasses.co.za/Home/WesternCape/Passes/WESTCOAST/GifbergPass/tabid/257/Default.aspx Gifberg]

Isoetes toximontana is an herb which grows in shallow water, very often emerging above the surface. Leaves are 3-10 per plant, up to 42 mm long, elliptical in cross-section. Mega- and microsporophylls may be found on the same plant. Megaspores number up to 36 per sporangium, gray-green, drying olive green, each up to 320 μm in diameter, covered with tubercules (bumps) over most of the surface. Microspores are brown, up to 25 μm in diameter.{{cite journal |last1=Musselman |first1=Lytton John |last2=Roux |first2=J. P. |year=2002 |title=Isoetes toximontana (Isoetaceae), a New Quillwort with Green Megaspores from the Northern Cape of South Africa |journal=Novon |volume=12 |issue=4 |pages=504-507 |doi=10.2307/3393131 |jstor=3393131 |url=https://www.biodiversitylibrary.org/page/643083 |via=Biodiversity Heritage Library}}