GENUS 34. THISTLE FAMILY. 435 
34. MACHAERANTHERA Nees, Gen. & Sp. Ast. 224. 1832. 
Annual, biennial or perennial branched herbs, with leafy stems, alternate, mostly serrate 
or pinnatifid leaves, the teeth or lobes usually bristle-tipped, and large heads of both tubular 
and radiate flowers. Involucre of numerous series of imbricated canescent or glandular 
bracts with herbaceous or foliaceous spreading or appressed tips. Receptacle alveolate, the 
alveoli usually toothed or lacerate. Ray-flowers numerous, violet to red or purple, pistillate. 
Disk-flowers perfect, their corollas tubular, 5-lobed, yellow, changing to red or brown; 
anthers exserted, appendaged at the tip, rounded at the base; style-appendages subulate to 
lanceolate. Achenes turbinate, narrowed below, pubescent. Pappus of numrous stiff, rough 
unequal bristles. [Greek, sickle-anther.] 
About 15 species, natives of western North America. Type species: Machaeranthera ‘anaceti- 
folia (H.B.K.) Nees. 
Annual or biennial ; leaves pinnatifid. 1. M. tanacetifolia. 
Perennial or biennial ; leaves sharply serrate. 2. M. sessiliflora. 
1. Machaeranthera tanacetifolia (H.B.K.) 
Nees. Tansy Aster. Dagger-flower. 
Fig. 4359. 
Aster tanacetifolius H.B.K. Nov. Gen. Sp. 4: 95. 1820. 
M. tanacetifolia Nees, Gen. & Sp. Ast. 225. 1832. 
Annual or biennial; stem glandular-pubescent, 
often viscid, densely leafy, much branched and 
bushy, 1°-2° high. Leaves sessile or short-petioled, 
pubescent, the lowest 1-3’ long, 2-3-pinnatifid, their 
lobes linear or oblong, acute or mucronate, the up- 
per pinnatifid, those of the branches sometimes en- 
tire; heads numerous, corymbose-paniculate, 1-2’ 
broad; involucre hemispheric, 4-6” high, its bracts 
linear, glandular, imbricated in 5-7 series, their green 
tips Very squarrose; rays 15-25, violet-purple, 5’-8” 
long, pappus copious, tawny; achenes villous. 
In dry soil, South Dakota to Nebraska, Texas, Mex- 
ico, Montana and California. June—Aug. 
WN 
2. Machaeranthera sessiliflédra ( Nutt.) 
Greene. Viscid Aster. Fig. 4360. 
os sessiliflora Nutt. Trans. Am. Phil. Soc. 7: 301. 
1840. 
Af. sessilifiora Greene, Pittonia 3: 60. 1896. 
Stem usually stout, finely rough-pubescent or ca- 
nescent, branched, and viscid-glandular above, 1°-2° 
high. Leaves lanceolate, linear, or the lowest spatu- 
late, sessile, somewhat viscid, sharply incised-dentate, 
the larger 17-3’ long, the teeth bristle-tipped; heads 
numerous, racemose, or corymbose above, 17-13’ 
broad, the lower often nearly sessile; involucre broad- 
ly turbinate or hemispheric, 4’—6” high, its bracts 
acute, imbricated in 6-Io series, their tips strongly 
squarrose; rays numerous, violet, 4’-6” long; pap- 
pus copious; achenes narrow, appressed-pubescent. 
In dry soil, central and western Nebraska and Colo- 
tado. July—-Oct. 
A Kansas plant differs from this species by having 
acute appressed tips to the involucral bracts. 
35. ERIGERON L. Sp. Pl. 863. 1753. 
Branching or scapose herbs, with alternate or basal leaves, and corymbose, paniculate or 
solitary, peduncled heads of both tubular and radiate (rarely all tubular) flowers. Involucre 
hemispheric, cylindric or campanulate, its bracts narrow, nearly equal, mostly imbricated in 
but 1 or 2 series. Receptacle nearly flat, usually naked. Ray-flowers. in our species. white, 
violet or purple, pistillate. Disk-flowers yellow, tubular. perfect, their corollas mostly 5-lobed. 
Anthers obtuse and entire at the base. Style-branches more or less flattened, their appendages 
short, mostly rounded or obtuse. Achenes flattened. usually 2-nerved. Pappus-bristles fragile, 
slender, scabrous or denticulate, in 1 series, or often an additional outer short series. [Greek, 
early-old, alluding to the early hoary pappus.] 
