Page:Popular Science Monthly Volume 81.djvu/320

314 tissues, accompanied by the agglomeration of the contained rubber. The methods of the chemist have suggested extraction by the use of suitable solvents, the rubber being recovered by differential solution and distillation of the solvents. Both these methods have been adapted to the extraction of rubber from the plant which shall claim brief attention in what follows.

I refer to the guayule, a low, gray or greenish-gray shrub (Figs. 1 and 2).

of limited distribution within the Chihuahuan desert, having the center of its geographical area very near to the northern boundary of the state of Zacatecas, Mexico. The southern extension of this area lies somewhat below San Luis Potosi; to the north it is found in the Big Bend country of Texas; here are rather small amounts, and of low stature as compared with the conditions farther to the south. The plant scarcely invades the state of Sonora, and is found only in the western part of Nuevo Leon.

The chief interest attaching to its occurrence in Texas is the fact that it was here first discovered by Dr. J. M. Bigelow "near Escondido (Hidden) Creek." The party of the Mexican Boundary Survey, of which Bigelow was a member, in all probability rested at the large spring which forms the source of this creek, a camping-place for uncounted generations of Indians before the days of the white man. Here, on the McKenzie ranch, east of Fort Stockton, the writer also