MOXOPETALOUS EXOGENOUS PLANTS. 331 



roughened, contracted below the middle; heads often ra- 

 cemose on the short lateral branches. Stem l°-3° high; 

 leaves l'-2' (in the var. 3-6') long; heads showy. 



*♦ Leaves (and sterna) smooth, the lowest tapering into a petiole, the others sessile or 

 clasping ; heads middle-sized, showy ; scales of the obovoid involucre whitish, 

 the s/iort green tips scarcely spreadin-g ; rays bright blue ; achenia mostly 

 smooth. 



A. CONCINNUS, Willd. Stem nearly smooth, somewhat 

 loosely corymbose ; the branches virgate, dichotomous-pa- 

 niculate ; leaves lanceolate, partly clasping, remotely and 

 sharply serrate, -with scabrous margins, those of the branch- 

 lets oblong, entire; scales of the involucre linear, acute, 

 closely imbricated. Stem 2°-3° high; achenia pubescent. 



*** Lower leaves large, cordate, on long petioles ; heads middle-sized or small, ra- 

 cemed or panicled ; scales of the involucre somewhat membranaceous, with 

 short green tips ; rays blue or violet. 



t Leaves entire, or nearly so. 



A. UNDULATUS, L. Pubescent ; stem racemose-panicled 

 above ; leaves varying from lanceolate to broadly ovate, 

 often wavy or slightly serrate on the margins, roughish on 

 the upper surface, the lowest on long and slender petioles 

 which are dilated and clasping at the base, the upper on 

 broadly winged petioles or sessile and clasping; scales of 

 the obovoid involucre linear, appressed, acute. Stem 2°-3° 

 high ; heads small ; rays pale blue. 



A. ASPERULUS, Torr. and Gray. Koughish ; stem race- 

 mose-panicled above, or simple ; lowest leaves oblong-ovate, 

 obtuse or slightly cordate at the base, sparingly serrate, on 

 slender (not clasping) petioles; the upper oblong, narrow- 

 ed at the base, sessile or on short winged petioles; those of 

 the branches minute ; lieads loosely racemed or panicled, 

 small; scales of the hemispherical involucre lanceolate, 

 acute. Stem 2° high ; rays pale blue. 



