240 
2, A. Canadensis Michx. Smooth, or hoary with silky down, 3 to 6 dm. high: 
lower leaves twice-pinnately divided, the upper 3 to 7-divided, the divisions linear, 
rather rigid: heads rather large, in panicled racemes.—A far northern and Rocky 
Mountain species, found in Texas on the “ Staked Plains.” 
3. A. redolens Gray. Radical branches whitish tomentulose, otherwise green 
and glabrous (or nearly so): leaves 3 to 5-parted into linear subentire segments: 
heads 3mm. high, ina long erect panicle: involucre glabrous.—A species of the 
Chihuahua Mountains (Pringle), “on cool slopes under cliffs,” and discovered in the 
Chisos Mountains of southwestern Texas (Nealley). Said to have ‘a powerful odor, 
like that of A, Absinthium but stronger, which burdens the air of the whole hillside” 
(Pringle, in Gray, Proc, Am, Acad.,, 21), 
+ + Leaves entire or some 8-cleft. 
4, A. dracunculoides Pursh. Tall, 6 to 15 dm. high, somewhat woody at base, 
slightly hoary or glabrous: leaves linear and entire, or the lower 3-cleft: heads 
small and numerous, panicled.—A common and polymorphous species of the north- 
ern plains, extending into northern and western Texas. 
5, A. filifolia Torr. Suffruticose, finely canescent, 3 to 9 dm. high: leaves all fili- 
form, the lower commonly 3-parted: heads very small and numerous, crowded in a 
long leafy panicle.—A species of the northern plains, extending to New Mexico and 
the western borders of Texas. 
* * Receptacle smooth : flowers all fertile, a few pistillate, the others perfect : branching 
perennials 8 to 15 dm. high. 
6. A. Ludoviciana Nutt. Whitened woolly throughout: leaves lanceolate, the 
upper mostly entire, the lower usually cut-lobed, toothed or pinnatifid, the upper 
surface sometimes glabrate and green: heads mostly sessile in narrow panicles, — 
Extending from the northern plains through Texas to Mexico. 
7. A. Mexicana Willd. Less woolly-tomentose, and the involucre canescent or 
glabrate: leaves narrow-lanceolate to linear, some 3 to 5-cleft or parted, the lower 
(radical) cuneate, incisely pinnatifid or trifid: heads very numerous in an ample loose 
panicle, many pedicellate.—Extending from the dry plains of Arkansas through 
Texas to Arizona and Mexico. Variously referred to 4. Ludoviciana and A, vulgaris, 
** * Receptacle hairy: flowers all fertile, the marginal ones pistillate, 
8. A. frigida Willd. Low, 15 to 50 em. high, in tufts, slightly woody at base, 
white-silky: leaves pinnately parted and 3 to 5-cleft, the divisions narrow-linear: 
heads globose, racemose.—Mountains and plains of western Texas. 
106. PSATHYROTES Gray. 
Low and pubescent annuals (scapose in ours), with round-cordate or 
ovate petioled leaves, rather small many-flowered discoid heads of yel- 
lowish perfect and fertile flowers, lax involucral bracts in 2 series, flat 
naked receptacle, terete obscurely striate villous or hirsute achenes, 
and pappus of copious very unequal rather rigid obscurely denticulate 
bristles shorter than the corolla and fuscous or rusty at least in age. 
1. P. scaposa Gray. Leaves all at or near the base, ovate or roundish, almost en- 
tire, at first loosely white-tomentose, at length glabrate: scapes or naked peduncles 
several, 7.5 to 10 cm. high, bearing 3 to 7 corymbosely disposed heads, glandular- 
pubescent: achenes hirsute: pappus about half as long as corolla.—Borders of Texas 
near Kl Paso. 
107. BARTLETTIA Gray. 
Slender almost glabrous annual, with slender-petioled roundish 
leaves, many-flowered radiate heads with yellow flowers all fertile, lax 
involucral bracts in 2 or 3 series (the inner and larger membranaceous), 
