4 Guayule. 



in the Gray Herbarium of Harvard University. A reproduction of this 

 specimen is here given (plate 2, fig. A) . The name in the right-hand corner 

 is in the writing of Professor Gray. The label is Bigelow's field label. Fol- 

 lowing is the description published in the "Botany of the Boundary," 

 p. 86, 1859 : 



Parthenium argentatum ( sp. nov. ) : fruticosum, pube brevi appressima 

 sericeo-incanum ; foliis spathulato-lanceolatis oblongisve in petiolum longe attenu- 

 atis parce dentatis seu laciniatis sub-triplinerviis ; ramulis floridis elongatis nudis 

 oligocephalis ; involucri squamis obtusissimis ; acheniis sericeis; pappo e paleis 

 2 membranaceis lanceolatis. Near Escondido Creek, Texas, in rocky places, 

 Sept., 1852; Dr. Bigelow. A well-marked species, connecting the sections Argy- 

 rochaeta and Parthenichaeta ; the leaves and branches whitened with a very fine 

 and close silk-silvery pubescence, which appears to be wholly or nearly persistent . 

 Leaves one to two inches long, including the tapering base and petiole; 2 to 5 

 lines wide, mostly acute, scarcely veined, beset on each margin with from one to 

 three salient teeth, or sharp lobes. Flowering branchlets slender, 4 to 8 inches 

 long, nearly leafless and peduncle-like, bearing 3 to 7 sub-sessile heads (as large 

 as those of P. incanunt) in a cluster. Exterior scales of the involucre short, orbic- 

 ular-ovate; the inner orbicular, scarious-membranaceous. Paleae of the pappus 

 lanceolate or oblong-lanceolate, rather narrower and less obtuse than in P. hyster- 

 ophorus, puberulent, the inner edge more or less adnate to the base of the broadly 

 obovate and cucullate emarginate ligule. l (Fig. 9.) 



As will be seen, the crowding of the heads to form a "cluster" de- 

 pends upon external conditions. In a later description published by 

 Gray in the "Synoptical Flora," 2 we find the first hint of the peculiarity 

 which later brought it into economic prominence. This description is 

 as follows: 



P. argentatum Gray. Suffrutescent, a foot high, silvery-canescent with close 

 tomentum; branches erect, rather leafless above, bearing comparatively large and 

 few heads (of 2 lines in diameter) ; leaves lanceolate to spatulate in outline, some 

 entire or incisely 2-3 toothed, the larger incisely pinnatified into 2 to 7 acute 

 lateral lobes; pappus a pair of lanceolate chaffy awns (Bot. Mex. Bound., 86; 

 Southwest border of Texas, Bigelow; Adj. Mex., Parry, Palmer; produces a gum 

 or resin in Mexico). 



THE VULGAR NAME. 



The name 3 " guayule " is properly applied only to Parthenium argen- 

 tatum Gray. On account, however, of a superficial resemblance it has to 

 certain other plants, especially because of similarities in size and in the 

 gray color (so often seen in the desert) of the foliage, these have been 

 wrongly called by the same name. 4 The mariola (P. incanum H. B. K., 

 plate 44, fig. B), a closely related species, is one of these; and its very 

 general association with the guayule proper has led to much error in 

 estimating acreage of guayule. It is of interest in this connection to note 

 that the mariola is known to the peon, in some parts at any rate, as 

 "hembra de guayule," 5 apparently because of the very constant associ- 



1 Gray, in Torrey, Botany of the Boundary, U.S. and Mex. Boundary Surv., 

 p. 86, 1859, 



'Synoptical Flora of North America, vol. i, pt. 2, p. 245, 1886. 

 'Investigated by Endlich, 1905. 



4 The name is also applied to Crysactinia mexicana Gray, and more recently 

 also to Euphorbia misera, material of which was sent to Dr. J. N. Rose, of the 

 U. S. National Herbarium, from southern California, on the supposition that it 

 contained rubber. 



5 The female guayule. 



