262 COMPOSITAE. 



391. PSILOCARPHUS. 



Low woolly annuals; leaves entire, mostly opposite; heads 

 small, discoid, many-flowered, in terminal capitate clusters and 

 in the forks of the branches, surrounded by the upper leaves; 

 fertile flowers numerous, in several series on the globular chaffy 

 receptacle; pappus none; akene loose in the bladder-like bract, 

 oblong or narrower, slightly compressed. 



Heads sparsely covered with long loose woolly hairs. P. elalior. 



Heads covered with short close wool. P. oreganus. 



Psilocarphus elatior Gray. Erect and simple or more commonly branched 

 from the base and spreading, 5-10 cm. high, loosely white- woolly throughout; 

 leaves lanceolate or linear-spatulate, 1-2 cm. long; heads 6-8 mm. broad, 

 subtended by leaves; fruiting bracts appressed, tomentose; akenes cylindrical. 

 Common in low ground, especially dried-up ponds. 



Psilocarphus oreganus Nutt. Stems ascending, 2-5 cm. high; leaves 

 narrowly oblanceolate, 8-10 mm. long; heads covered with close wool; bracts 

 2 mm. long; akenes cylindric. In dried-up ponds, Spokane County. 



392. CHRYSANTHEMUM. 



Herbs; heads many- flowered ; ray-flowers usually elongated, 

 numerous, pistillate; disk-flowers usually all fertile; involucre 

 hemispherical or flatter, the scales more or less scarious, short- 

 appressed, imbricated in several rows; receptacle flat or convex, 

 naked; pappus none; disk-corollas often flattened or 2-winged 

 below, 4- or 5-toothed ; akenes short, nearly terete, several ribbed 

 or angled, truncate at apex. 



Chrysanthemum leucanthemum pinnatifidum Lecoq. & Lemotte. Oxeye 

 Daisy. Perennial, erect, 30-60 cm. high, glabrous or nearly so, usually simple; 

 basal leaves oblong or spatulate, incisely pinnatifid or toothed; cauline smaller, 

 sessile and partly clasping, linear; heads 3-5 cm. broad, on long naked pe- 

 duncles; involucral-bracts oblong-lanceolate, obtuse, rusty at tip; rays 20-30, 

 white; akenes many-ribbed, pappus none. Sparingly introduced. 



393. ACHILLEA. 



Perennial herbs, rather strong-scented; leaves alternate, ser- 

 rate or pinnately dissected; heads small, in corymbs, many- 

 flowered; flowers yellow, white or sometimes rose-colored, all 

 fertile; ray-flowers few or several, mostly short or broad, pis- 

 tillate; involucre narrow, the scales imbricated in a few rows, 

 appressed; receptacle flattish to conical, with thin chaff; pappus 

 none; akenes oblong or ovate, obcompressed, surrounded by a 

 narrow and cartilaginous margin. 



Achillea milleiolium lanulosa (Nutt.) Piper. Yarrow or Milfoil. Peren- 

 nial, erect, usually tufted, 30-60 cm. high, loosely pubescent throughout with 

 white somewhat woolly hairs; basal-leaves short-petioled, oblong or oblong- 

 lanceolate, 8-20 cm. long, pinnately divided into very numerous segments; 



