Genus 17.] 



THISTLE FAMILY. 



327 



17. OONOPSIS Greene, Pittonia, 3: 45. 1896. 



Perennial herbs, the following species glabrous, mostly tufted, with woody roots, the 

 stems leafy to the top. Leaves entire, linear to lanceolate. Heads cymose at the end of 

 the stem or branches. Involucre campanulate to ovoid, its bracts flat, imbricated in severa 

 series, herbaceous, cuspidate, appressed and erect, or the outer spreading. Disk-flowers with 

 a nearly cylindric 5- toothed corolla. Stamens and style included or scarcely exserted. Ray- 

 flowers present or wanting, pistillate. "Style-appendages ovate to subulate. Achenes gla- 

 brous, or somewhat pubescent. Pappus-bristles coarse, rigid. [Greek, resembling an egg, 

 referring to the ovoid involucre.] 



Four known species, natives of central North America. 



i. Oonopsis Engelmanni (A. Gray) Greene. Engelmann's Oonopsis. 



(Fig. 3664.) 



Bigelovia Engelmanni A. Gray, Proc. Am. Acad. 

 11: 75. 1S76. 



Oonopsis Engelmanni Greene, 

 1896. 



Pittonia, 3: 45. 



Perennial by a deep woody root, glabrous 

 throughout; stems stiff, about S' high, densely 

 leafy. Leaves narrowly linear, sessile, 9 // -i8 // 

 long, less than i // wide, brittle when dry; heads 

 clustered, or sometimes solitary at the ends of 

 the branches, yi ; wide or less, sessile among the 

 upper leaves; involucre oblong-campanulate, 

 its bracts in about 4 series, oblong to spatulate, 

 short-acuminate or mucronate, appressed; ray- 

 flowers none; disk-flowers about as long as the 

 rather rigid capillary pappus-bristles; achenes 

 linear-oblong, narrowed at the base, many- 

 striate. 



Western Kansas and Nebraska. Sept.-Oct. 



18. PRIONOPSIS Nutt. Trans. Am. Phil. Soc. (II) 7: 329. 1841. 



A glabrous annual or biennial herb, leafy to the top, with sessile spinulose-dentate leaves, 

 and large heads of yellow radiate and tubular flowers. Involucre broadly hemispheric, its 

 bracts imbricated in several series, lanceolate, acuminate, the outer more or less spreading. 

 Receptacle naked. Disk-flowers perfect, their corollas 5-toothed. Ray-flowers very numer- 

 ous, pistillate. Achenes glabrous, those of the ray-flowers broader than those of the disk; 

 pappus of a few deciduous rigid unequal bristles, the outer very short. [Greek, resembling 

 a saw, referring to the leaf-margins.] 



A monotypic genus of south-central United States. 



i. Prionopsis ciliata Nutt. Prionopsis. 

 (Fig. 3665.) 



Donia ciliata Nutt. Journ. Acad. Nat. Sci. Phila. 2: 118. 



1821. 

 Aplopappus ciliatus DC. Prodr. 5: 346. 1836. 

 Prionopsis ciliata Nutt. Trans. Am. Phil. Soc. (II) 7: 



329. 1841. 



Stem erect, stout, branched, very leafy, 2-5 

 high. Leaves sessile, oval or the lower obovate, 

 obtuse, conspicuously veined, \ f -jf long, j4 / -ij4 / 

 wide, sharply serrate with bristle-pointed teeth; 

 heads few, clustered, stalked or nearly sessile, i / - 

 i}4 / broad; involucre depressed-hemispheric, its 

 bracts glabrous; achenes of the ray-flowers ellip- 

 soid, those of the disk-flowers oblong, the central 

 sterile; pappus-bristles rigid, the inner ones rough 

 or ciliate. 



On hillsides and river-banks, Missouri and Kansas to 

 Texas. Aug.-Sept. 



