1520 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM 



1. Parthenium argentatum A. Gray in Torr. U. S. & Mex. Bound. Bot. 86. 

 1859. 

 Parthenium lloydii Bartlett, Torreya 16: 46. 1916. 



Coahuila and Durango to Zacatecas and San Luis Potosi. Texas; type from 

 Escondido Creek. 



Shrubby, up to 1 meter high, much branched; branches silvery-strigillose ; 

 petioles 0.5 to 2.5 cm. long; blades lanceolate to lance-ovate, 1 to 4.5 cm. long, 

 0.3 to 2.5 cm. wide, acute or acuminate, acute at base, coarsely few-lobed to 

 entire, silverj'-canescent; heads several, in small long-peduncled cymes or 

 cymose panicles, short-pediceled, about 6 mm. wide; pappus of 2 divergent or 

 erectish awns about 1 mm. long. "Guayule" (the most common and widely 

 distributed name); "hierba del hule" (Durango); "tataninf" (Otomi); "hierba 

 blanca," "hierba ceniza" (Querctaro); "hule" (Zacatecas, Chihuahua); "copa- 

 llin," "afinador" {Lloyd); "xihuite," ''jihuite" (Zacatecas). 



According to Patoni, the name "guayul" or "guauyul," of which guayule is a 

 variant, belongs properly to Vauquelijiia corymhosa (see page 323), and became 

 applied through some error to this plant. 



The guayule rubber plant is one of the most important members of the Mexican 

 flora. Its stems yield a high percentage of rubber, a fact well known to the early 

 inhabitants. From the plant was obtained the rubber for making the large balls 

 used in the game of pelota, a game of very ancient origin. 



Attempts at industrial exploitation of the plant began in Zacatecas as early 

 as 1892 or 1893, and shortly afterward in San Luis Potosi, but these were not 

 successful financially on account of the lack of suitable apparatus for the extrac- 

 tion of the rubber, and because of the absence of a market. About 1904, when 

 much capital from the United States had been invested in the industry, it became 

 of importance and large factories were established for the treatment of the plant. 

 The raw plant rose to a price of $75 per ton. In 1911 the outlay of North Ameri- 

 can capital alone in the industry was said to be $30,000,000, and between July 1, 

 1905, and July 1, 1909, about 32,000,000 pounds of guayule rubber were imported 

 into the United States, this being about 80 per cent of the total export. Later 

 the industry declined, partly because of a failure in supply, but chiefly on account 

 of the competition of East Indian rubber. 



The following references may be mentioned here: F. Altamirano, Datos para 

 la historia y explotaci6n del "Guayule," Boletfn de la Secretaria de Fomento de 

 M6xico II. 5: 1098-1123. 1906; R6mulo Escobar, El guayule y su propagacion, 

 Boletfn de la Secretaria de Fomento 24. 1910; J. E. Kirkwood, Propagation of 

 guayule by seeds, Amer. Rev. Trop. Agr. 1: 34-43. 1910; Kirkwood, The hfe- 

 historj' of Parthenium argentatum (guayule), Amer. Rev. Trop. Agr. 1: 193-205. 

 1910. 



2. Parthenium parviceps Blake, Contr. U. S. Nat. Herb. 22: 607. 1924. 



Known only from the type locality. Barranca de Tenampd,, Zacuapan, Veracruz. 



Suffrutescent or frutescent; stem arachnoid-tomentose; leaf blades triangular- 

 ovate, 5.5 to 9 cm. long, 3.5 to 6 cm. wide, acute, canescently arachnoid-tomentose 

 beneath. 



3. Parthenium fruticosum Less, in Schlecht. & Cham. Linnaea 5: 152. 1830. 

 Chiapas and Veracruz (?); type from Plan del Rio, Veracruz (?). 

 Apparently suffrutescent and tall; stem sordidly pilose-tomentose; leaf blades 



triangular-ovate, about 10 cm. long, 7.5 cm. wide, obtuse, truncate-rounded at 

 base, green above, cinereous-tomentulose beneath, on narrowly margined petioles 

 1.5 cm. long. 



4. Parthenium schottii Greenm. in Millsp. & Chase, Field Mus. Bot. 3: 109. 



1904. 

 Yucatdn; type from Progreso. 



