LOASA FAMILY 133 



Family 100. LOASACEAE. 



LoASA Family. 



Erect, climbing herbs, often clothed with barbed, stinging or viscid hairs. Leaves 

 alternate or opposite, without stipules. Flowers racemose or cymose, regular and 

 perfect. Hypanthium adnate to the ovary, turbinate to cylindric. Sepals 4-5, im- 

 bricate or convolute. Petals 4—5 or apparently 10, yellow or red. Stamens 5 to many, 

 usually arranged in clusters opposite the petals ; outer filaments sometimes dilated or 

 becoming staminodia and passing into petals ; anthers introrse, longitudinally de- 

 hiscent. Ovary 1 -celled (rarely 2-3-celled), with 2-5 parietal placentae; styles 

 slender, entire or 2-3-lobed. Ovules anatropous. Fruit a capsule; seeds solitary or 

 usually numerous, with scanty endosperm. 



About IS genera and 250 species, all but one, natives of North America. 



Stamens 5; seed solitary. , 1. Petalonyx. 



Stamens many; seeds several to many. 



Style entire or 3-cleft; ovary with 3 placentae. 2. Mentzelia. 



Style 5-cleft; ovary with 5 placentae. 3. Eucnide. 



1. PETALONYX A. Gray, Mem. Amer. Acad. 5 : 319. 1854. 



Low desert shrubs or at least woody at base, the stems brittle and the whole plant 

 rou^h with barbed hairs. Leaves alternate, entire or toothed, petioled or sessile. Flowers 

 in terminal spicate or head-like racemes. Hypanthium minute, cylindric. Sepals 5, linear, 

 deciduous. Petals 5, with long very slender connivent claws and spreading blades. Sta- 

 mens 5, the slender filaments protruding between the claws in bud up to the base of the 

 overlapping blades which cover the anthers until anthesis. Ovary 1-celled; style entire, 

 exserted; ovule solitary, pendulous. Capsule very small, irregularly dehiscent; seeds 

 oblong, smooth. [Name Greek, meaning petal and claw.] 



A genus of 4 species, natives of the arid southwestern United States and northern Mexico. Type species, 

 Petalonyx Thurberi A. Gray. 



Leaves sessile, dull and cinereous. 



Leaves and young branches scabrous with short stiflF hairs; bracts toothed at base. 1. P. Thurberi. 



Leaves and young branches clothed with soft spreading villous hairs concealing the interspersed short stiff 

 ones 2. P. Gilmanii. 



Leaves petioled, shining. 



Leaves round-ovate; bracts 7-8 mm. long. 3. P. nitidus. 



Leaves oblong-lanceolate; bracts 5-7 mm. long. 4. P. linearis. 



1. Petalonyx Thurberi A. Gray. Common Sandpaper Plant. Fig. 3276. 



Petalonyx Thurberi A. Gray, Mem. Amer. Acad. 5: 319. 1854. 



Stems with erect branches from a more or less woody base, 4-6 dm. high, retrorsely pubescent. 

 Leaves ovate to linear-lanceolate, 1-2 cm. long, sessile and more or less clasping at base, entire 

 or with a few teeth toward the base, gray-green on both surfaces with short, stiff barbed hairs ; 

 flowers in short dense spikes ; bracts ovate, acuminate, toothed toward the base ; petals light 

 yellow, about 5 mm. long, hispid on the back ; stamens about twice the length of the petals ; 

 capsule 2 mm. long. 



Dry desert washes and hillsides, Lower Sonoran Zone; Mojave and Colorado Deserts, California, to southern 

 Nevada, Arizona, Sonora and Lower California. Type locality: Valley of the Gila River, Arizona. Dec^July. 



2. Petalonyx Gilmanii Munz. Death Valley Sandpaper Plant. Fig. 3277. 



Petalonyx Gilmanii Munz, Leaflets West. Bot. 2: 69. 1938. 



Diffusely branched shrub, up to 1 m. high and about as broad, the short stiff barbed hairs 

 concealed by interspersed longer spreading soft villous hairs both on the leaves and the young 

 branches, older branches whitish with exfoliating papery bark. Leaves broadly ovate, cordate- 

 clasping at base, those of the principal branches 1-2 cm. long, entire, acute or abruptly short- 

 acuminate at apex; flowers in short dense terminal spikes; bracts thin, greenish becoming straw- 

 colored in age, sessile, subcordate, 4-7 mm. long, pubescent with short stiff hairs; sepals mem- 

 branous, linear-lanceolate, 2 mm. long, pubescent ; petals white, 3-4 mm. long, pubescent on the 

 back ; stamens well exserted. 



Desert washes. Lower Sonoran Zone; vicinity of Death Valley, Inyo County, California. Type locality: 

 Ryan Wash, Death Valley. May-June. 



3. Petalonyx nitidus S. Wats. Shining Sandpaper Plant. Fig. 3278. 



Petalonyx nitidus S. Wats. Amer. Nat. 7: 300. 1873. 



Petalonyx Thurberi var. nitidus M. E. Jones, Contr. West. Bot. No. 12: 16. 1908. 



Low desert shrub, much branched, 25-45 cm. high, young branches short-pubescent and 



