S1
Critically Imperiled
Microthelys rubrocallosa (Green Medusa Orchid)
Perennial herb; roots tuberous, 1-5, clustered, 0.2-1.4 cm in diameter; leaves deep blue-green, 1-2 (6), emerging prior to, or with, the inflorescence and fading shortly after anthesis (McVaugh [1985] observed leafless flowering plants bearing wither...
Muhlenbergia villiflora var. villosa (Hairy Muhly)
Rhizomatous perennial; stems much branched above, wiry, 4-30 cm tall, usually growing in isolated clumps and seldom forming dense stands; blades short, less than 3 cm long, strongly involute; inflorescence a narrow contracted panicle, 1-5 cm long, us...
Panicum mohavense (Mohave Panicum)
Annual, much branched at base, 2-8 cm tall; culms erect, with 1 node, papillose-pilose, mostly obscured by the leaves; leaves with prominently veined, papillose-pilose sheaths; ligules 0.2 mm long, membranous and with short hairs; blades 1-4 cm long,...
Paronychia wilkinsonii (Wilkinson's Nailwort)
Small, cushion-forming perennial herb with a branched caudex; stems erect or ascending, 2.5-6(-10) cm high, hirtellous, mostly obscured by the opposite leaves; stipules lanceolate, scarious, 5-8 mm long and generally equaling the leaves, to 1.5 mm wi...
Pediocactus knowltonii (Knowlton Cactus)
Stems 1.0-2.5 cm in diameter, solitary or a few in a cluster, barely protruding above ground level; tubercles not grooved; spines about 20 per areole, all radials, radiating from areole and appressed to the plant, 1-2 mm long, usually whitish, pinkis...
Pediomelum pentaphyllum (Chihuahua Scurfpea)
Perennial herb up to about 25 cm tall, grayish-hairy with straight hairs that lie against the surface of the foliage; stems with a thin, cord-like, easily broken, subterranean portion bearing a few small bracts, and a very short aerial, leafy portion...