gracefully, branched in the upper head-bearing portion, the branches in turn bear- 

 ing very many short-bearing branchlets which are often ascending; leaves alternate, 

 sessile, not lobed. the louer portions occasionally narrowed to a subpetiolar base; 

 heads rarely more than 1 cm. long; receptacle fiat or slightly convex, not chaffy; 

 involucres usually narrowly campanulate; phyllaries in a few series, graduated, 

 usually linear-lanceolate or linear, mostly stramineous and chaffy in texture with 

 a slightly darker more herbaceous median strip which is slightly dilated near the tip; 

 ray flowers pistillate and fertile, several in number (in one species only 2 per 

 head), with yellow rays; disk flowers perfect and fertile, with yellow corollas; 

 pappus simple, of numerous essentially equal capillary bristles; achenes many- 

 ribbed, nearly terete. 



SoUdago is a large North American genus (with one species also in Europe). It 

 is one of our more difficult genera probably because of rampant hybridization. 



1. Head-bearing branchlets few, borne on short branches about as long as to 

 shorter than the remote upper serrate leaves from whose axils they 

 arise 1. S. caesia. 



1 . Head-bearing branchlets usually borne on branches longer than the leaves 



from whose axils they arise (2) 



2(1). Plants perfectly smooth and glabrous, leaves fleshy or thinner, entire and 

 with inconspicuous venation or merely with finely reticulate pattern, 

 rarely with easily visible secondary nerves; basal leaves ascending, 

 often long and grasslike; head bearing portion of the plant often 

 elongate and slender but definitely one-sided and its branches nearly 

 always curly at the tip 3. S. sempervirens. 



2. Plants usually pubescent, if nearly glabrous then the leaves usually with 2 



fairly conspicuous lower secondary nerves and/ or not entire margin 

 and/or not at all grasslike (3) 



3(2). Upper half of the stem roundly quadrangular, the ridges usually narrowly 

 winged 2. S. salicina. 



3. Upper half of stem not quadrangular nor 4-winged (4) 



4(3). Leaves of midstem ovate, 1.3 to 2.5 times as long as broad, the lower sur- 

 faces with conspicuous and prominent pale network of nerves, each 

 side with 10 to 20 rather evenly spaced conspicuous marginal 

 serrations 4. S. rugosa. 



4. Leaves of midstem mostly proportionally longer and narrower or if only 2.5 



times as long as broad then broadest in the upper half and/ or the 

 lower surfaces with less prominent nervation, the margins usually 

 with fewer teeth or the teeth concentrated toward the tip (5) 



5(4). Most of the foliage and stems closely pubescent with microscopic hairs, 

 making parts of the plant cinereous or sordid green; stems 6-20 dm. 

 tall 5. S. altissima. 



5. Most of the foliage and stems glabrous and yellowish or pale-green with the 



exceptions of the margins of the leaves and often scattered pubes- 

 cence in narrow lines on the upper part of the stem or upper part 

 scabro-hirtellous (in S. spathulata) (6) 



6(5). Plants with mostly short and stout rhizome or caudex; plants 5-20 cm. 

 tall 8. S. spathulata. 



6. Plants with well developed creeping rhizomes; plants 5-25 dm. tall (7) 



7(6). Leaves punctate; inflorescence ample in small glomerules, copiously leafy- 

 bracteate 7. S. occidentalis. 



7. Leaves not punctate; inflorescence corymbiform; stem glaucous, becoming 



definitely puberulent in the inflorescence 6. S. gigantea. 



1611 



