432 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



KEY TO THE GENERA. 



oa 5; plants covered with stinging hairs 1. Cevallia (p. 432). 



Stamens numerous; plants rough-hispid with barbed or 

 hooked but never stinging hairs. 

 Placenta; with horizontal lamellae between the seeds; 



seeds flat, winged 2. Nuttallia (p. 432). 



Flacenta; without lamellae; seeds not winged. 



Seeds prismatic, muricate; leaves sessile 3. Acrolasia (p. 435). 



Seeds pyriform or ellipsoid, striate with parallel 

 curved lines; leaves petiolate (petioles some- 

 times very short) 4. Mentzelia (p. 436). 



1. CEVALLIA Las. 



Canescent branched perennial herbs armed with stinging hairs; leaves alternate, 

 sessile, sinuate-pinnatifid; flowers in terminal heads; tube of the calyx short, with 

 erect linear lobes; petals 5, plumose; stamens 5, erect, with very short filaments; fruit 

 dry, indehiscent, 1-seeded. 



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



Type locality: Mexico. 



Range: Western Texas to southern Arizona and southward. 



New Mexico: Rincon; mesa west of Organ Mountains; Dog Spring; Lake Valley; 

 Lordsburg; Hatchet Ranch. Dry mesas, especially along arroyos, in the Lower Sono- 

 ran Zone. 



2. NUTTALLIA Raf. 



Herbaceous short-lived perennials (sometimes annuals) with white stems, at first 

 rough, becoming smooth and shining below, or the epidermis exfoliating; leaves simple, 

 alternate, more or less densely rough-hirsute with stiff, barbed or hooked, white hairs; 

 hypanthium mostly campanulate, becoming hemispheric to cylindric in fruit; sepals' 

 5, persistent; petals 5 or with 5 additional petal-like staminodia, of some shade of yel- 

 low (often described as white); stamens numerous, the outer rows of filaments often 

 petaloid; capsules 1 -celled with parietal placenta? lamellated between the flattened, 

 winged, finely tuberculate 6eeds. 



KEY TO THE SPECIES. 



Leaves pinna tely toothed or lobed. 



Lobes of the leaves linear, several times as long as broad, 1 to 2 

 mm. wide. 

 Plants small, 30 to 50 cm. high; flowers pale yellow, small. 1. JV. gypsea. 

 Plants taller, spreading, 60 to 80 cm. high; flowers deep 



golden yellow, larger 2. JV. laciniata. 



Lobes of the leaves oblong, hardly more than twice as long as 

 broad, 2 to 3 mm. wide. 

 Petals bright yellow; some of the leaves entire. 



Some of the leaves oblanceolate; plants stout; capsules 



nearly as broad as long 12. JV. integra. 



All leaves linear; plants slender; capsules twice as long 



as broad 13. JV. springeri. 



Petals whitish or pale yellow; leaves all lobed or toothed. 

 Lobes of the leaves few, 1 to 3 on each side, often en- 

 tirely wanting; plants cespitose 3. JV. perennis. 



