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Big Galeta

Pleuraphis rigida
(Hilaria rigida)

Pleuraphis rigida, Big Galeta, Pen & Ink © by Michael Plagens

Sketched from live specimen in Butler Valley, La Paz County, AZ. 06 April 1993.

PERENNIAL GRASS: This long-lived grass takes on a shrub-like morphology with multiple above ground branches and woody (lignized) lower stems and reaching a height of 1 m.

close-up view of spikelets, Pleuraphis rigida FLOWERS: A narrow spike on a twisty stem consisting of closely appressed spiklets appearing three per node. A series of short awns on each spikelet.

LEAVES: Leaf-blades are cauline, i.e. dispersed along stems as opposed to not restricted to base as in many grasses.

RANGE: Fairly common in the Sonoran Desert of Arizona on plains, sand dune areas, and adjacent to washes. Also ranges into Mojave and Chihuahuan Deserts.

FRUIT: A grain.


Family: Poaceae

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In Rainbow Valley, Maricopa Co., Arizona, Sept. 2009, I found many P. rigida blooming and setting seed. About every fifth plant had seed heads infected with and swollen-black by infection of smut, Ustilago sp. fungus. Another smut fungus occurs on Bermuda Grass (Cynodon dactylon).

Pleuraphis rigid,Big Galeta, Photo of spikelet infected with a smut fungus © by Michael Plagens

Smut fungus (Ustilago) in a grain of P. rigida. The mature spores fill the seed hull which ends up growing several times larger than usual. The spores are black, appearing like soot. Photographed in s.w. Maricopa Co., Arizona, USA. Sept. 2009.

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Copyright Michael J. Plagens, 1999-2010