86 UNITED STATES AND MEXICAN BOUNDARY. 
一 下 ea 
smaller than those of the disk. The fertile ovaries, at least the one or two which make the * 
longer and subulate achenia, begin to elongate soon after anthesis, and to project to twice or 
thrice the length of the involucre. The scales of the latter subtend the fertile flowers, but do 
not inclose or embrace them. Pales of the receptacle much smaller than the involucral scales, | 
linear, plane, forming a circle between the ray and the disk, one subtending each sterile flower. | 
Sterile style barely bidentate at the apiculate tip. The longer achenia, which usually persist 
after the fall of the involucre, etc., are from 3 to 41 lines long, (excluding the awns,) barely 
half a line in thickness, slightly obcompressed, even, not at all margined, tipped with two 
stout, diverging or sometimes recurved-spreading, smooth, rigid, inarticulated and persistent, 
subulate awns, of 14 to 3 lines in length. There is usually only one such achenium to each 
capitulum. The others are shorter and thicker, and tuberculate-rugose inside, but otherwise 
similar, or one of them barely 2 lines long, oblong, truncate at both ends, the apex bearing t wo 
very short and divaricate or almost obsolete awns or horns. 
PARTHENIUM INCANUM, H. B. K.; Gray, Pl. Wright, 1, р. 103, & 2, p. 85. Р. ramosissimum, 
DC. Prodr. 5, p. 532. From the Pecos to Cobre, etc.; Bigelow, Wright, Schott. On the Rio 
Grande, below Mount Carmel; Parry. 
PARTHENIUM ARGENTATUM (sp. nov.): fruticosum, pube brevi appressima sericeo-incanum ; 
foliis spathulato-lanceolatis oblongisve in petiolum longe attenuatis 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- 
rocheta and Parthenicheta; the leaves and branches whitened with a very fine and close silky- 
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. incanum) in a cluster. Exterior scales of the involucre short, orbicular- 
ovate; the inner orbicular, scarious-membranaceous. Paleæ of the pappus lanceolate or oblong- | 
lanceolate, rather narrower and less obtuse than in P. Hysterophorus, puberulent, the inner | 
edge more or less adnate to the base of the broadly obovate and cucullate emarginate ligule. | 
PARTHENIUM HYSTEROPHORUS, Linn. Texas, etc.; common in low places. 
ет РАВТНЕМІСЕ MOLLIS, Gray, Pl. Wright, 2, p. 85. Near Santa Cruz, Sonora; Wright, Thurber. 
EuPHROSYNE AMBROSLEFOLIA, Gray, Pl. Wright, 1, р. 102, & 2, p. 85. Near Conde’s Camp, New 
Mexico; Wright. Cook's Springs; Bigelow. | 
Iva DEALBATA, Gray, Pl. Wright, 1, p. 104. Leon Springs; Bigelow. Lagunas de Patos, 
Chihuahua; Thurber. 
— r 
DICORIA, Torr. & Gray, in Emory, Rep., 1848, p. 143. 
Capitulum monoicum; floribus foemineis 2 in ambitu, masculis 8-12 in disco. Involucrum 
patulum, duplex, exterius e phyllis 5 ovalibus herbaceis uniseriatis, interius e squamis 2 orbicu- 
latis tenuiter scariosis planis mox accrescentibus, utraque florem femineum fulerante. Recepta- 
culum parvum, planum, paleis angustis lineari-spathulatis inter flores. Fl. Foem. Corolla 
nulla: stylus alte bifidus, ramis linearibus glabris. Fl. masc. Corolla obconica, 5-dentata. | л 
Anthere vix coalite, sed flamentis monadelphis. Stylus abortivus in synemate apice 5-dentato 
