STANDLEY TREES AND SHRUBS OF MEXICO 1521 



Shrub; stem tuberculate-hispidulous or tuberculate-pilose; leaf blades triangular- 

 ovate, 5 to 9.5 cm. long, 2 to 5.5 cm. wide, acute or obtuse, repand, finely tuber- 

 culate above, beneath finely strigillose, hispidulous, or rarely rather densely 

 puberulous, on margined petioles 1 to 2 cm. long; awns 2 or 3, short, erect or 

 recurved. "Santa Maria," "chalcha." 



5. Parthenium tomentosum DC. Prodr. 5: 532. 1836. 

 Puebla and Oaxaca; type collected between Oaxaca and Mitla. 



Shrub 3 meters high; stem tomentose, glabrescent; leaf blades triangular- 

 ovate, 2.5 to 10 cm. long, 1.6 to 6.5 cm. wide, cordate or subtruncate at base, 

 green or cinereous above, cinereous-tomentulose and -veiny beneath, on nearljr 

 marginless petioles 0.6 to 3 cm. long. 



6. Parthenium stramonium Greene, Pittonia 4: 240. 1901. 

 Parthenium arctium Bartlett, Proc. Amer. Acad. 44: 635. 1909. 

 Sonora and Chihuahua; type from Chuichupa, Chihuahua. 



Shrub about 3.5 meters high; stem cinereous-tomentulose, glabrescent; leaf 

 blades triangular-ovate, 10 to 30 cm. long, 3 to 10 cm. wide, subcordate and usually 

 unequal at base, weakly repand to crenulate, green or at first finely cinereous- 

 tomentulose above, finely cinereous-tomentulose beneath. 



7. Parthenium incanum H. B. K. Nov. Gen. & Sp. 4: 260. pi. 391. 1820. 

 Parthenium ramosissimum DC. Prodr. 5: 532. 1836. 



Sonora to Coahuila, south to Hidalgo; type from Botanic Garden of Mexico. 

 Texas to Arizona. 



Low shrub; stem cinereous-tomentose, glabrescent; leaf blades 1.5 to 6 cm. 

 long, usually cinereous but sometimes green above, cinereous-tomentulose 

 beneath; pappus awns 2, divergent, about 1 mm. long. "Mariola" (the usual 

 and most widely dispersed name); "hembra de guayule" (so called because it 

 often grows with the true guaj'ule); "tananinf" (Queretaro); sometimes known 

 erroneously as "guayule." 



This plant furnishes rubber like that of guayule, but in smaller amounts. 

 It has been employed extensively in Mexico for the extraction of commercial 

 rubber, and was known also to the aboriginal inhabitants. Children sometimes 

 chew the stems to obtain the rubber for making balls. In Coahuila the plant is 

 reported to be used as a domestic remedy for affections of the liver. 



8. Parthenium lozanianum Bartlett, Proc. Amer. Acad. 44: 636. 1909. 

 Known only from the type locality. Hacienda El Carrizo, Sierra Madre, above 



Monterrej'^, Nuevo Le6n. 



About 2.5 meters high; leaf blades 4 to 9 cm. long, 2 to 4.5 cm. wide, deltoid- 

 ovate, somewhat trilobate, coarsely repand-dentate with blunt teeth, usually 

 with a pair of small lobes below base of blade. 



42. IVA L. Sp. PI. 988. 1753. 



Reference: Rydberg, N. Amer. FI. 33: 4-7. 1922. 

 1. Iva hayesiana A. Gray, Proc. Amer. Acad. 11: 78. 1876. 



Northern Baja CaUfornia and Cedros Island. California; type from San 

 Diego County, California. 



Frutescent, under 1 meter high; branches erectish, strigillose and glandular; 

 leaves opposite, oblong-obovate, elliptic-oblong, or spatulate, 5 cm. long or less, 

 usually obtuse, entire, short-petioled, thick, triplinerved; heads small, disciform, 

 nodding, yellowish, 3 to 6 mm. wide, in virgate racemes or racemiform panicles, 

 bracted with small leaves; phyllaries few, obovate, obtuse, herbaceous, punctate; 

 pistillate flowers with short tubulose corolla; hermaphrodite flowers sterile; 

 anthers free, with inflexed appendages; achenes obovoid, obcompressed , epap- 

 pose. 1.8 mm. long. 



