COMPOSITAE (COMPOSITE FAMILY) 553 



-toothed ligules. Bracts of the involucre flattened on the back below, with 

 abruptly dilated thin margins infolded so as to inclose the ray-achene. Re- 

 ceptacle broad and flat, bearing a series of thin chaffy bracts between the ray- 

 and disk-flowers. Achenes of the ray obcompressed, almost always smooth, 

 destitute of pappus; those of the disk similar or more linear-cuneate, mostly 

 pubescent, bearing a pappus of 10-20 bristles or scales, or rarely none. 



1. Layia glandulosa H. & A. Bot. Beech. 350. 1833. Stems 2-4 dm. high, 

 diffusely branched: lower leaves lanceolate or linear, laciniate-pinnatifid or 

 incised; the upper narrow and entire: rays 8-13, large and conspicuous (bright 

 white or tinged with rose), 8-14 mm. long, 3-lobed: villous hairs of the pappus 

 bristles copious, the outer straight and erect, the inner soon crisped and inter- 

 laced into a woolly mass. (Blepharipappus glandulosus Hook.) In barren 

 ground; chiefly west of our range. 



61. PSILOSTROPHE DC. 



Low and corymbosely branched woolly herbs, with alternate and spatulate 

 or linear leaves, the cauline entire, and small heads of yellow flowers. Bracts 

 of the involucre distinct, but connected by the intricate wool so as to seem con- 

 nate. Heads with 3 or 4 ray and 5-12 disk-flowers, all fertile. Involucre of 

 4-10 linear coriaceous woolly bracts, and a few smaller' scaripus ones within, 

 with sometimes an additional narrow outer one. Receptacle small, flat. 

 Ligules broad, abruptly contracted at base into a short tube, truncate and 

 2-3-lobed; disk-corollas with short externally glandular-bearded teeth. Pap- 

 pus of 4-6 hyaline scales. Riddellia. 



Pappus-scales oval, obtuse . 1. P. Bakeri. 



Pappus-scales lanceolate, acute . . . . . . . . 2. P. tagetina. 



1. Psilostrophe Bakeri Greene, PI. Baker. 3: 29. 1901. Herbaceous, per- 

 ennial, much-branched, 1-2 dm. high, the branches short, almost divaricate, 

 at earliest flowering not much exceeding the large, spatulate- obovate or 

 -oblong green but thinly villous-lanate basal leaves, which are obtuse, entire, 

 some of the cauline coarsely toothed or 3-lobed at or near the apex, all ob- 

 viously 1-3-nerved: heads large, apparently always 5-rayed and the rays 10-14 

 mm. long, deeply 3-lobed; bracts of involucre green-herbaceous, distinct, the 

 tips spreading: achenes glabrous, closely and strongly striate; scales of the 

 pappus obtuse, more or less toothed, little longer than broad, not half as long 

 as the achene. (P. pumila A. Nels. Proc. Biol. Soc. Wash. 16: 22. 1903.) 

 Western Colorado and Utah. 



2. Psilostrophe tagetina (Nutt.) Greene, Pitt. 2: 176. 1891. Loosely or 

 somewhat villosely lanate, sometimes glabrate in age, rather widely branched : 

 radical and even lower cauline leaves often laciniate-pinnatifid: heads nu- 

 merous, mostly cymosely clustered and short-peduncled : scales of the pappus 

 oblong-lanceolate, entire, usually more than half as long as the disk-corollas. 

 Riddellia tagetina. Southern Colorado (?) to Arizona and western Texas. 



62. PERICOME Gray 



Strong-scented yellow-flowered branching perennials, with long-acuminate 

 leaves. Head many-flowered, homogamous. Involucral bracts lightly con- 

 nate by their edges into a campanulate cup. Disk-corollas with viscous- 

 glandular tube and much exserted anthers. Achenes strongly villous-ciliate. 

 Pappus a lacerate-ciliate crown, and sometimes a pair of short awns, one from 

 each angle of the achene. 



1. Pericome caudata Gray, PL Wright. 2: 82. 1852. Leaves opposite, 

 long-petioled, green and minutely somewhat resinous-atomiferous, triangular- 

 hastate, 5-10 cm. long, with sparingly crenate-dentate or entire margins, 

 caudately long-acuminate, as also in less degree are the basal angles: heads 

 numerous in terminal corymbiform cymes, 9-12 mm. high; flowers golden- 



