6. Baccharis L. Groundsel-tree 



Unisexual shrubs or subshrubs, glabrous or hispid; branchlets usually striate- 

 angled or slightly striate and terete, smooth to glandular-scabrous; leaves subulate 

 to obovate, alternate, crowded to sparse, entire to serrate or dentate, 1- to 3- 

 nerved, sessile or petioled, usually reduced within the inflorescence (sometimes 

 to bractlike leaves); male and female heads on separate plants; heads in some- 

 what paniclelike, corymbiform or racemose aggregations; pistillate involucre hemis- 

 pheric to narrowly cylindric with outer phyllaries ovate to lanceolate; inner phyl- 

 laries lanceolate to narrowly linear and obtuse to acuminate, usually scarious- 

 margined, the midrib evident or obscure; receptacle pitted to nearly smooth, 

 naked or fimbrillate, flat; ray flowers absent; corolla filiform with 5 minute 

 distinct lobes or teeth, yellowish-white to brown in color; style bifurcate, style 

 branches usually glabrous; achene 5- to 10-ribbed, yellow to reddish, glabrous or 

 hispid, smooth or glandular; pappus of 1 to several series of numerous bristles, 

 flaccid or rigid, equaling or greatly exceeding the style; staminate involucre 

 hemispheric to cylindric with outer phyllaries ovate to lanceolate; inner phyllaries 

 lanceolate to linear and obtuse to acuminate, usually scarious-margined, the 

 midrib dilated and smooth or absent; receptacle pitted to nearly smooth, naked or 

 fimbrillate and flat; ray flowers absent; corolla filiform basally and either abruptly 

 or gradually enlarged and funnelform, white to yellowish-brown, its 5 lobes 

 lanceolate; style clavellate or bifurcate, its branches hispid; pappus not exceeding 

 style, usually one series of numerous bristles, rigid, more or less plumose-tipped, 

 the bristles more or less barbed, usually crisped; ovary abortive. 



Plants of this large genus (about 400 species, all American) unfortunately often 

 superficially resemble plants of other asterean genera, and their determination is 

 enigmatic until the unisexuality of the plants and flowers is discovered. 



1. Achenes 8- to 10-ribbed; leaves mostly less than 5 cm. long (2) 



1. Achenes 5-ribbed; leaves 5-12 cm. long (4) 



2(1). Leaves linear, entire, 25 mm. long or less; plants broomlike in appearance 

 1. B. sarothroides. 



2. Leaves oblong to obovate, mostly toothed, usually more than 30 mm. long; 



plants not broomlike (3) 



3(2). Fertile heads hemispheric, 5-10 mm. broad 3. B. salicina. 



3. Fertile heads cylindric or long-campanulate, 3-5 mm. broad 



2. B. Emoryi. 



4(1). Heads in a terminal large corymbiform aggregation; leaves 3-8 (-11) cm. 

 long, 10 (-20) mm. broad, not crowded 4. B. glutinosa. 



4. Heads in several smaller corymbiform aggregations terminating lateral 



branches; leaves 3-5 cm. long, 5 mm. broad, usually crowded 



5. B. viminea. 



1. Baccharis sarothroides Gray. 



Glutinous shrub 1-4.5 m. tall; branchlets conspicuously striate-angled, densely 

 fastigiately branched, often crowded into broomlike masses; leaves on young 

 rapidly growing branches linear to lance-linear, 1-2.5 cm. long, 1.5-3.5 mm. wide, 

 acute at both ends, somewhat leathery, entire, early deciduous, those of the 

 branchlets reduced to minute bracts 1-2.5 mm. long; heads numerous, solitary 

 or in few-headed glomerules at tips of branchlets; pistillate heads about 1 cm. 

 long at anthesis; phyllaries in several series, narrowly ovate to oblong, or oblong- 

 lanceolate, slightly granular-glutinous on exposed portions, margins scarious, 

 slightly erose toward the tips; receptacle essentially flat, alveolate but naked; 

 pistillate corollas nearly filiform, about 3 mm. long; achenes about 2 mm. long, 



1606 



