FLOWERING PLANTS AND FERNS OF ARIZONA 589 



mostly brittle and with pale exfoliating bark; leaves alternate, simple 

 but often deeply pinnatifid; flowers perfect, regular or nearly so, in 

 terminal inflorescences or some of them solitary in the forks of the 

 branches; calyx tube completely adnate to the ovary, only the 5 Lobes 

 or teeth free; petals yellow or yellowish, inserted on the calyx throat; 

 stamens few to many; fruit a 1-celled capsule, indehiscent or tardily 

 and irregularly dehiscent; seeds 1 to many. 



This family is remarkable for the diversity and peculiar structure 

 of the hairs. 



Key to the genera 



1. Ovary of 1 carpel, 1-celled, containing a single pendulous ovule; stamens 5 or 

 fewer (2). 

 2. Filaments very short, linear; anthers large, 2-celled, the connective produced 

 into a hyaline spoon-shaped body longer than the anther cell.-. 



1. Cevallia. 



2. Filaments elongate, filiform; anthers small, 4-celled, the connective not 



conspicuously produced 2. Petaloxyx. 



1. Ovary of more than one carpel, each carpel containing several to many ovules 

 borne on parietal placentas; stamens 10 or more (3). 



3. Carpels usually 3; placentas narrow or flat, not projecting far into the cavity 



of the ovary; ovules in 1 or 2 rows on the placenta; leaf blades not cordate 



at base 3. Me xtzelia. 



3. Carpels commonly 5; placentas thick, more or less circular in cross section, 

 projecting far into the cavity of the ovary and connected with the ovary 

 wall by a thin plate; ovules in several rows on the placenta; leaf blades 

 subcordate at base, round-ovate, crenate-dentate, rather thick. 



4. Eucxide. 



1. CEVALLIA 



Plant herbaceous, perennial, canescent, also hispid with stinging 

 hairs; leaf blades sinuate-pinnatifid; flowers small, in dense narrow- 

 bracted heads; calyx tube short, the calyx lobes and the petals similar 

 and seemingly in one series, long, narrow, erect, plumose with white 

 hairs. 



1. Cevallia sinuata Lag. ; Var. Cienc, 21: 35. 1805. 



Greenlee County to Cochise County, 4,000 to 5,000 feet, dry mesas 

 and slopes, August to November. Western Texas to southeastern 

 Arizona and northern Mexico. 



A noteworthy plant because of the stinging hairs and the peculiar 

 structure of the flowers. 



2. PETALOXYX. Saxdpaper-plaxt 



Plants woody, at least at base, the herbage scabrous; leaf blades 

 entire or dentate; flowers small, in short broad-bractcd spikes, the 

 petals whitish or pale yellow. 



Key to the species 



1. Leaves broad at base, sessile, not shiny, lanceolate to ovate, often few-toothed; 

 plant somewhat woody at base; herbage gray, very scabrous, densely his- 

 pidulous with retrorse hairs; floral bracts triangular-ovate, denticulate 



toward the base; petals 4 to 6 mm. long 1. P. thurberi. 



1. Leaves narrowed at base or short-petioled; plants woodv well above the 



base (2). 



2. Leaves sessile or nearly so, lance-oblong, 3 to 6 mm. wide, entire, green, 



muricate-scabrous, not shiny; inflorescences suboa pirate in flower, 



elongate in fruit; floral bracts ovate-cordate, entire, obtuse, densely 



soft-pubescent; petals 4 to 5 mm. long 2. P. lixearis. 



