854 CONTEIBUTIONS FROM THE NATIONAL HERBARIUM. 



115. LOASACEAE. Loasa Family. 



Usually herbs but sometimes slirubs; leaves opposite or alternate, entire or 

 toothed, estipulate; flowers perfect, racemose or cymose-paniculate, the pedi- 

 cels bibracteolate ; calyx tube adnate to the ovary, the limb 4 or 5-lobate ; petals 

 4 or 5, inserted in the calyx throat ; stamens few or numerous ; style subulate, 

 entire or bifid or trifid ; fruit a 1-celled capsule, containing 1 to many seeds. 



Several other genera are represented in Mexico by herbaceous species. Some 

 of them are plants with stinging hairs. Gevallia sinuata Lag. is a common 

 plant of the desert regions of northern Mexico, with hairs which sting as pain- 

 fully as those of a nettle. 



Leaves mostly opposite ; stamens numerous ; capsule many-seeded. 



1. MENTZELIA. 

 Leaves alternate; stamens 4 or 5; capsule 1-seeded 2. PETALONYX. 



1. MENTZELIA L. Syst. Nat. ed. 10. 1076. 1759. 



Several other representatives of the genus occur in Mexico, but they are 

 herbs. The leaves in most species of this genus are extremely scabrous and 

 cling tenaciously to clothing. Some of the species are known in the United 

 States by the name of "stickleaf." 



1. Mentzelia conzattii Greenm. Proc. Amer. Acad. 32: 298. 1897. 



Oaxaca. 



Tall shrub, sometimes 7 meters high, with brittle woody stems; leaves 

 mostly opposite, short-petiolate, lanceolate, 4 to 12 cm. long, acuminate, finely 

 dentate, scabrous above, tomentose beneath ; flowers pedicellate, cymose-panicu- 

 late, about 5 cm. broad, bright yellow ; calyx lobes 5, 12 to 15 mm. long ; petals 

 oblong-obovate, acute ; stamens numerous ; capsule about 1 cm. long and nearly 

 as thick. "Arnica." 



The leaves and roots, Professor Conzatti states, are employed as a remedy 

 for itch and other cutaneous diseases. 



2. PETALONYX A. Gray, Mem. Amer. Acad. n. ser. 5: 319. 1855. 



Low shrubs or herbs; leaves alternate, entire or toothed, sessile, very 

 scabrous ; flowers very small, in dense terminal bracted spikes or racemes ; 

 calyx tube short, the lobes 4 or 5, narrow, deciduous ; petals 4 or 5, clawed ; 

 stamens 4 or 5; staminodia none; fruit small, fragile, rupturing irregularly, 

 1-seeded. 



Leaves strongly revolute, crenate 1. P. crenatus. 



Leaves not revolute, entire or dentate. 



Leaves lanceolate or ovate, broad at base, often dentate 2. P. thurberi. 



Leaves linear or linear-oblanceolate, attentuate at base, entire_3. P. linearis, 



1. Petalonyx crenatus A. Gray; S. Wats. Proc. Amer. Acad. 17: 358. 1882. 

 Coahuila ; type from San Lorenzo de Laguna. 



Plants woody at base, the stems retrorse-hispidulous ; leaves oblong, 4 t<> 

 8 mm. long, obtuse, retrorse-scabrous ; flowers white, racemose ; petals 3 Uy 

 4 mm. long. 



2. Petalonyx thurberi A. Gray, Mem. Amer. Acad, n, ser. 5: 319. 1855. 

 Baja California and northern Sonora. Arizona, Nevada, and southern Cali- 

 fornia ; type from the Gila River, Arizona. 



Plants 1 meter high or less, chiefly or wholly herbaceous, very scabrous; 

 leaves 1 to 4 cm. long, thick and stiff, spreading or appressed, the upper 

 ones entire ; racemes 4 cm. long or shorter ; petals about 4 mm. long. 



