458 LOASACEAE, (Von. Il. 
Family 81. LOASACEAE Reichenb. Consp. 160. 1828. 
Loasa FAaMILy. 
Erect or Climbing branching herbs, often armed with hooked stinging or 
viscid hairs, with alternate or opposite exstipulate leaves, and solitary racemose 
or cymose, regular and perfect, white yellow or reddish flowers. Calyx-tube 
adnate to the ovary, its limb 4—5-lobed, persistent. Petals 4-5, inserted on the 
throat of the calyx. Stamens o, inserted with the petals; filaments filiform, 
commonly arranged in clusters opposite the petals; anthers introrse, longitud- 
inally dehiscent. Ovary 1-celled (rarely 2—-3-celled), with 2—3 parietal placentae; 
style filiform, entire or 2—3-lobed; ovules anatropous.. Capsule usually 1-celled, 
crowned with the calyx-limb. Seeds mostly numerous; endosperm scanty. 
About 13 genera and 200 species, all but 1 natives of America. 
1. MENTZELIA L, Sp. Pl. 516. 1753. 
Erect herbs, sometimes woody, with alternate entire lobed or pinnatifid leaves, and ter- 
minal solitary or cymose usually showy flowers. Calyx-tube cylindric, obconic or club- 
shaped, its limb generally 5-lobed. Petals 5 or 10, spreading, convolute in the bud, decidu- 
ous. Stamens 20-300. Ovary I-celled; 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. [Named in honor of C. Mentzel, a German botanist, died 1701. ] 
About 50 species, natives of western America. Besides the following, some 25 others occur in 
the western parts of North America. 
Flowers 5'’-10'' broad, yellow. 
Leaves, at least the lower, petioled; stem very rough; calyx-lobes 3'’ long. 1. MW. oligosperma. 
Leaves sessile; stem little rough; calyx-lobes 2"’ long. 3. MW. albicaults. 
Flowers 134'-4' broad. 
Flowers yellowish-white, opening in the evening. 
Flowers 1%'-2' broad; calyx-tube usually bractless. 
Flowers 3'-4' broad; calyx-tube usually bracted. 
Flowers bright yellow, opening in sunshine, 
. M. nuda, 
. M. decapetala. 
. M. laevicaulis. 
np 
1. Mentzelia oligospérma Nutt. Few-seeded Mentzelia. (Fig. 2517.) 
Mentzelia oligosperma Nutt. in Bot. Mag. i. 
1760. 815. 
Mentzelia aurea Nutt. Gen. 1: 300, 1818. 
Rough and viscid-pubescent, 1°-3° high. 
Leaves ovate or oval, coarsely dentate or sinu- 
ate, acute or obtusish at the apex, 1/-3/ long, 
the upper rounded or truncate at the base and 
sessile, the lower narrowed at the base and 
usually petioled; flowers yellow, 5//-10’’ broad, 
axillary or somewhat cymose, opening in sun- 
shine; petals 5, oblong-cuneate, acute, about 
twice as long as the linear-lanceolate calyx- 
lobes; filaments 20-30, all filiform; capsule 
linear, 6’’-8’’ long, few-seeded; calyx-lobes 
about 3’” long; seeds oblong, wingless. 
Prairies, Illinois to Kansas and Colorado, south 
to Louisiana, Texas and Mexico. May-July. 
2. Mentzelia nuda (Pursh) T. & G. Bract- 
less Mentzelia. (Fig. 2518.) 
Bartonia nuda Pursh, Fl. Am. Sept. 328. 1814. 
Mentzelia nuda T. & G. Fl. N. A. 1: 535. 1840. 
Rough with minute pubescence, slender, 1°-5° high, 
the stems light-colored. Leaves all sessile, lanceolate or 
oblong lanceolate, acute at the apex, usually sharply and 
deeply dentate, or the upper pinnatifid, 17-3’ long; flow- 
ers terminal and axillary, yellowish white, 1'%4/—2’ broad, 
opening in the evening; petals 10, about twice as long as 
the lanceolate calyx-lobes; calyx-tube usually not bract- 
eolate; stamens 100 or more, the outer ones somewhat 
petaloid; capsule oblong, 9’’-12’’ long, about 3’ thick; 
seeds numerous, wing-margined. 
Plains, Dakota to Kansas, Colorado and Texas. July-Aug. 
