642 FLORA. 



Petals 5 or 10, spreading, convolute in the bud, deciduous. Stamens 20-300. 

 Styles 3, more or less united; stigmas small, obtuse. Capsule dehiscent at the 

 summit, few-many-seeded. Seeds flat and sometimes winged, roughened, or 

 smooth. [In honor of C. Mentzel, a German botanist, died 1701.] About 50 

 species, natives of America. Besides the following, some 25 others occur in west- 

 ern N. Am. 



Flowers 1-2 cm. broad, yellow. 



Leaves, at least the lower, petioled; stem very rough ; calyx-lobes 6 mm. long. 



1. M. oligospermia. 

 Leaves sessile; stem little rough; calyx-lobes 4 mm. long. 3. M. albicaulis. 



Flowers 3-10 cm. broad. 



Flowers yellowish white, opening in the evening. 



Flowers 3-5 cm. broad ; calyx-tube usually bractless. 2. M. nuda. 



Flowers 7-10 cm. broad ; calyx-tube usually bracted. 4. M. decapetala. 



Flowers bright yellow, opening in sunshine. 5. M. laevicaulis. 



1. Mentzelia oligosperma Nutt. Few-seeded Mentzelia. (I. F. f. 2517.) 

 Rough and viscid-pubescent, 3-9 dm. high. Leaves ovate or oval, coarsely den- 

 tate or sinuate, 2-8 cm. long, the upper rounded or truncate at the base and 

 sessile, the lower narrowed at the base; flowers axillary or somewhat cymose, 

 opening in sunshine; petals 5, oblong-cuneate, acute, about twice as long as the 

 linear-lanceolate calyx-lobes; filaments 20-30, all filiform; capsule linear, 

 12-16 mm. long, few-seeded; seeds oblong, wingless. Prairies, 111. to S. Dak., 

 Kans., Colo., La. and Mex. May-July. 



2. Mentzelia nuda (Pursh) T. & G. Bractless Mentzelia. (I. F. {, 

 2518.) Rough with minute pubescence, slender, 3-15 dm. high, the stems light- 

 colored. Leaves lanceolate or oblong-lanceolate, acute, usually sharply and 

 deeply dentate, or the upper pinnatifid, 2-8 cm. long; petals 10, about twice as 

 long as the lanceolate calyx-lobes; calyx-tube usually not bracteolate; stamens 100 

 or more, the outer ones somewhat petaloid; capsule oblong, 1.5-2/5 cm. long, 

 about 6 mm. thick; seeds numerous, wing-margined. Plains, S. Dak. to Kans., 

 Colo, and Tex. July-Aug. 



3. Mentzelia albicaulis Dougl. White-stemmed Mentzelia. (I. F. f. 

 2519.) Stem nearly white, shining, 1. 5-5 dm. high. Leaves mostly lanceolate, 

 sinuate-pinnatifid, sinuate-lobed, or the upper and lower sometimes entire, rough 

 with short stiff hairs, 2-8 cm. long; flowers few together at the ends of the branches, 

 or also axillary, 1-2 cm. broad, short-pedicelled or sessile; calyx-lobes linear- 

 lanceolate; capsule linear, 2.5 cm. long or less, many-seeded; seeds angled, tuber- 

 culate, wingless. Neb. to Br. Col., Cal. and N. Mex. May-July. 



4. Mentzelia decapetala (Pursh) Urban & Gilg. Showy Mentzelia. 

 (I. F. f. 2520.) Roughish-pubescent, stout, seldom over 6 dm. high. Leaves oval, 

 lanceolate or oblong, acute or acuminate, sinuate-pinnatifid, 5-15 cm. long, the 

 upper sessile, the lower petioled ; flowers mostly solitary, terminal; petals 10, about 

 twice as long as the lanceolate calyx-lobes; filaments all filiform, very numerous 

 (200-300); capsule oblong, 3-5 cm. long; seeds numerous, margined, not winged. 

 Plains, Dak. and Mont, to Neb. and Tex. June-Sept. 



5. Mentzelia laevicaulis (Dougl.) T. & G. Smooth-stemmed Mentzelia. 

 (I. F. f. 2521.) Stout, 6-12 dm. high, minutely pubescent, or the stems at length 

 glabrate and whitish. Leaves sessile, lanceolate or ovate-lanceolate, sinuate- 

 pinnatifid, acute or acuminate, 2-8 cm. long; flowers mostly solitary, terminal, 

 7-10 cm. broad; calyx-tube bractless; petals 5, or with 5 additional narrower inner 

 ones. 2-3 times as long as the calyx-lobes; stamens very numerous; capsule oblong, 

 about 2.5 cm. long; seeds numerous, winged, minutely tuberculate. Plains and 

 dry soil, Neb., Mont, and Wyo. to Ore., Utah and Cal. June-July. 



Order 24. OPUNTIALES. 



Fleshy plants, with continuous or jointed stems, leafless, or with small 

 leaves, generally abundantly spiny, the spines developed from cushions 

 of minute bristles (areolae). Flowers mostly solitary, sessile, perfect, 



