THE MOST IMPORTANT SPECIES. 17 



practiced on those trees, is here out of the question. A more rational 

 method of preparation would consist in cutting the plants near the 

 ground, after which they would be passed between rollers and the 

 rubber extracted by chemical or mechanical means with the aid of 

 water. It is possible that, by using properly constructed machinery, 

 the fiber as it comes from the mill could be processed and utilized in 

 manufacturing low-grade fabrics, or if this is not feasible, the crushed 

 residue would furnish material for the manufacture of paper-pulp. 



ASCLEPIAS SUBULATA (DESERT MlLKWEED). 



Description. Plant a rounded perennial herb, woody at base in 

 some types, 3 to 8 feet high, 2 to 6 or even 10 feet broad when growing 

 in low places where water accumulates after rains, narrow and few- 

 stemmed when on dry upland slopes (this upland form is more woody 

 and may be a distinct race); roots deep, ending above in a much- 

 branched crown; stems usually 12 to 30 in poor plants, but up to 500 

 or more in robust forms, straight, either simple or with a few straight 

 branches, glabrous but with a gray bloom; leaves usually reduced to 

 linear, very acute scales 3 inches or less long, but more developed in 

 good seasons, and then often quite copious; flowers appearing after the 

 rains regardless of season, dull greenish white, in rounded clusters 

 which terminate erect or ascending branches of the inflorescence ; pods 

 from erect to pendent on curved stalks, fusiform, very slenderly taper- 

 ing to the apex, 3.5 to 6 inches long, 0.5 to 0.75 inch thick, smooth and 

 glabrous or only minutely puberulent. 



References. Torrey, Pacif. R. Rept., 5: 362, pi. 7, 1857. Gray, Syn. Fl., 2 1 :96, 1878. 



Distribution and ecology. This is preeminently a desert species, 

 although it ranges from southeastern California, western Arizona, and 

 western Sonora across Lower California to the islands off the west 

 coast. The northernmost known station is Searchlight, Nevada, 

 while to the east it extends but slightly beyond Florence, in south- 

 western Arizona. To the south it grows at least as far as Cape San 

 Lucas and Guaymas. At the latter place it is common and said to be 

 known as yumete. The only known station in upper California, 

 outside of the desert area, is Tecate Valley, near the Mexican border, 

 southeast of San Diego. Even within the area as thus delimited, A. 

 subulata nowhere occurs in great abundance. Usually it grows as 

 scattered clumps on the foothill slopes and in dry, stony stream ways, 

 which are flooded with storm-water for a short period after the infre- 

 quent rains. Occasionally the plants are found growing in better soil 

 of depressions where the water remains for some time. Here they 

 readily respond to the improved conditions and form large, bushy 

 plants, with a greatly increased number of stems. For example, at 

 Sentinel, Arizona, a few plants were found in such depressions which 



