GENUS 17. 



THISTLE FAMILY. 



377 



17. OONOPSIS [Nutt] Greene, Pittonia 3: 45. 1896. 



Shrubs or 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 several 

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

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

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

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

 to the ovoid involucre.] 



Four known species, natives of central North America. Type species : Oonopsis multicaulis 

 (Nutt.) Greene. 



i. Oonopsis Engelmanni (A. Gray) Greene. Engelmann's Oonopsis. Fig. 4206. 



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

 75- 1876. 



Oonopsis Engelmanni Greene, Pittonia 3 : 45. 1896. 



Perennial by a deep woody root, glabrous 

 throughout; stems stiff, about 8' high, densely 

 leafy. Leaves narrowly linear, sessile, g"-2 f long, 

 less than i" wide, brittle when dry; heads clus- 

 tered, or sometimes solitary at the ends of the 

 branches, I' 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, Nebraska and Colorado. 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 S-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. 4207. 



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, con- 

 spicuously veined, i'-3' long, i'-ii' wide, sharply ser- 

 rate with bristle-pointed teeth; heads few, clustered, 

 stalked or nearly sessile, i'-i*' broad; involucre de- 

 pressed-hemispheric, its bracts glabrous; achenes of 

 the ray-flowers ellipsoid, 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. 



