Genus 64.] 



THISTLE FAMILY. 



427 



16. Helianthus decapetalus L,. Thin- 

 leaved or Wild Sunflower. (Fig. 3913.) 



Helianthus decapetalus L- Sp. PI. 905. 1753. 



Perennial by branched, sometimes thickened 

 rootstocks; stem slender, glabrous or nearly so, 

 branched above, i-5 high; branches puberulent. 

 Leaves thin or membranous, $'-8' long,-i/-3 / wide, 

 ovate or ovate-lanceolate, the lower all opposite 

 and slender-petioled, the upper commonly alternate, 

 all usually sharply serrate, roughish above, finely 

 but often sparingly pubescent beneath, acuminate, 

 the rounded or truncate base decurrent on the peti- 

 ole; heads numerous, 2 / ~y broad; involucre hemi- 

 spheric, its bracts linear-lanceolate, acuminate, 

 hirsute, ciliate, spreading, often longer than the 

 yellow disk; rays 8-15, light yellow; chaff entire or 

 3-toothed, pubescent at the apex; achenes glabrous; 

 pappus of 2 subulate awns. 



In moist woods and along streams, Quebec to Michi- 

 gan, south to Georgia and Kentucky. Aug.-Sept. 



17. Helianthus tracheliifolius Mill. 

 Throatwort Sunflower. (Fig. 3914.) 



Helianthus tracheliifolius Mill. Gard. Diet. Ed. 8, No. 7. 

 1768. 



Similar to the following species, but the stem usually 

 roughish-pubescent. Leaves short-petioled, ovate-lan- 

 ceolate, 3-nerved near the base, green both sides, but 

 darker above, generally rougher on the upper sur- 

 face, the lower ones sharply serrate; branches and pe- 

 duncles scabrous; heads several, lYz'-^Yz' broad; bracts 

 of the hemispheric involucre linear-lanceolate, long- 

 acuminate, ciliate and puberulent, longer than the yel- 

 low disk, sometimes foliaceous, and 3 times its length. 



In dry soil, Pennsylvania and Ohio to Wisconsin. 

 Aug.-Sept. 



18. Helianthus strumosus L,. Pale- 

 leaved Wood Sunflower. (Fig. 3915.) 

 Helianthus strumosus L- Sp. PI. 905. 1753. 



Perennial by branched, sometimes tuberous- 

 thickened rootstocks; stem glabrous below, some- 

 times glaucous, 3-7 high, branched above, the 

 branches usually pubescent. Leaves short-petioled, 

 ovate or ovate-lanceolate, not membranous, rough 

 above, pale and somewhat puberulent or canescent 

 beneath, serrate, serrulate, or nearly entire, acumi- 

 nate, contracted much below the middle and decur- 

 rent on the petiole, 3-nerved above the base, $'-8' 

 long, i/-2^ / wide, mostly opposite, the upper often 

 alternate; heads commonly several, 2}4 / ~4 / broad; 

 involucre hemispheric, its bracts lanceolate or ovate- 

 lanceolate, acuminate, ciliate, equalling or a little 

 longer than the diameter of the yellow disk; rays 

 5-15; chaff pubescent; achenes nearly glabrous. 



In dry woods and on banks, Maine and Ontario to Minnesota, Georgia and Arkansas. July-Sept. 

 Helianthus strumosus macrophyllus (Willd.) Britton, Mem. Torr. Club, 5: 335. 1894. 

 Helianthus macro phvllus Willd. Hort. Berol. pi. 70. 1806. 

 Helianthus mollis Willd. Sp. PI. 3: 2240. 1804. Not Lam. 1789. 

 H. strumosus var. mollis T. & G. Fl. N. A. 2: 327. 1842. 



Leaves finely and densely canescent beneath. Massachusetts to Penns3 T lvania and Iowa. 



