THISTLE FAMILY. 



Genus 36.] 



1. Leptilon Canadense (L.) Britton. 



Horse-weed. Canada Fleabane. 



(Fig. 3827.) 



Erigeron Canadensis L- Sp. PI. 863. 1753. 



Stem hispid-pubescent, or glabrate, $'-\o 

 high, the larger plants paniculately much 

 branched. Leaves usually pubescent or ciliate, 

 the basal and lower spatulate, petioled, incised, 

 dentate or entire, i' 4/ long, obtuse or acutish, 

 those of the stem linear and mainly entire; 

 heads usually very numerous; about 2 // broad; 

 involucre campanulate, l // -ij^ // high, its 

 bracts linear, acute, glabrate, the outer shorter; 

 rays numerous, white, shorter than the pappus 

 and mostly shorter than their tubes. 



In fields and waste places, a common weed 

 throughout North America except the extreme 

 north. Widely distributed as a weed in the Old 

 World and in South America. Called also Butter- 

 weed, Prideweed, Fireweed, Blood-staunch, Cow's- 

 or Colt's-tail, Bitter-weed. June-Nov. 



391 



2. Leptilon divaricatum (Michx.) Raf. 



Low Horse- weed. Purple Horse -weed. 



(Fig. 3828.) 



Erigeron divaricatus Michx. Fl. Bor. Am. 2: 123. 

 Leptilon divaricatum Raf. Fl. Tell. 2: 265. 1818. 



1803. 



Stem diffusely much branched, 3 / -i2 / high, pubes- 

 cent or hirsute. Leaves all linear or subulate, entire, 

 4 // -i2 // long, about y z " wide, the uppermost minute; 

 heads numerous, about 2" broad; involucre campanu- 

 late, i // high, its bracts linear, acute, pubescent, the 

 outer shorter; rays purplish, shorter than their tubes. 



In sandy soil, especial^ along rivers, Indiana to Minne- 

 sota, south to Tennessee, Louisiana, Nebraska and Texas. 

 June-Oct. 



37. DOELLINGERIA Nees, Gen. & Sp. Ast. 176. 1832. 



Perennial leafy herbs, the lower leaves reduced to scales or sheaths, the upper large, 

 mostly entire, acute or acuminate in our species. Basal leaves none. Heads corymbose, usu- 

 ally numerous; involucre campanulate to hemispheric, its bracts imbricated in several series, 

 appressed, thin, sometimes scarious-margined, their tips not herbaceous nor foliaceous. 

 Receptacle foveolate. Ray-flowers white, pistillate, not very numerous. Disk-flowers per- 

 fect, the corolla with a slender tube abruptly expanded into a campanulate 5-lobed limb, 

 white to greenish in our species. Anthers obtuse at the base; style-appendages ovate to sub- 

 ulate (rarely obtuse). Achenes obovoid, glabrous, or pubescent. Pappus double, the outer 

 series of numerous short bristles or scales, the inner series of long capillary bristles, some 

 or all of which have thickened tips. [In honor of Th. Dollinger, botanical explorer.] 



About 4 species, natives of eastern North America. 



Leaves lanceolate to ovate; heads mostly numerous. 



^Leaves lanceolate to oblong-lanceolate, acuminate. 1. D. umbellata. 



Leaves ovate to ovate-lanceolate, acute. 2. D. humilis. 



Leaves, at least the lower, obovate; heads commonly few. 3. D. infirma. 



