Mentzelia
(named after Christian Mentzel, 1622-1701, a German botanist). Including Eucnide and Microsperma. ORD. Loaseae. A genus of half-hardy, annual, biennial, or perennial, herbaceous plants, found chiefly in Mexico, California, and the Southern United States. Flowers orange or white, solitary, racemose or cymose, opening only during sunshine. Leaves alternate or nearly opposite, coarsely toothed. For culture, &c., see Bartonia (which genus is now generally included under the present one).
M. bartonioides (Bartonia-like).* fl. solitary, terminal; petals sulphur-yellow, paler, almost white beneath, ovate or rather obovate, slightly serrated, on long pedicels. Summer. l. ovate, acute, lobed and serrated. Stems about 1ft. long, flexuose, succulent, sub-translucent. Western United States, 1849. Annual. Eucnide bartonioides and Microsperma bartonioides (B. M. 4491) . M. hispida (hairy). fl. yellow; petals obovate, mucronately acuminate, longer than the calyx; stamens numerous. June and July. l. nearly sessile. h. 1 1/2ft. Mexico, 1820. Perennial. (B. M. 3205.) M. laevicaulis (smooth-stemmed). fl. bright yellow, from 2 1/2in. to 3in. across, expanding only in the morning, and closing after noon. Summer. h. 2ft. California. Biennial.
M. oligosperma (few-seeded). fl. yellow; petals acuminate; peduncles axillary, solitary. May and June. fr. reflexed. Stem branched. h. 2ft. Louisiana, 1812. Perennial. (B. M. 1760.) M. ornata (adorned).* fl. white, large, odoriferous, expanding after sunset, and remaining closed up the whole of the day. July to September. Ovary leafy; seeds naked. l. hispid, glandular, laciniate. h. 2ft. Missouri, 1811. Annual. (B. M. 1487, under name of Bartonia decapetala.)