Thistle Family. 73 



Boltonia. Heads many -flowered ; rays white or purpUh, disk yellow; pappus of a few 



short bristles and 2 -4 awns. 

 Aster. Heads usually small, many-flowered, on leafy peduncles; rays white, blue or 

 purple, disk yellow; involucre well imbricated, pappus simple, copious, of capillary 

 bristles; achenes flattish. 

 Erigeron. Heads many-flowered, on naked peduncles ; involucre b'lt little imbricated ; 

 pappus a single row of capillary bristles with intermixed smaller ones or with an 

 outer pappus of scales or little bristles; achenes flattened. 

 Tribe Irtuleae. Heads usually small, discoid, except in Inula where the 

 rays are large and yellow; anthers sagittate, unappendaged above, tailed be- 

 low; style-branches obtuse or truncate, naked: pappus capillary or none. 

 Our species have the receptacle not chaffy. 



Antennaria. Heads dioecious: pappus of the staminate flowers club-shaped, of the 



pistillate flowers united at the base and falling away together. 

 Anaph«lts. Heads dioeoious or polygamo-dioecious; pappus not club-shaped nor united 



at the base, 

 Gnaphalitjm. Heads with all the flowers fertile ; pappus capillary. 

 Inula. Heads large, many-flowered, with yellow rays; pappus of rough capillary 

 bristles. 

 Tribe Heliantheae. Heads radiate or discoid; involucre herbaceous or 

 foliaceous; receptacle chaffy; pappus a cup or crown, or awns, bristles or scales, 

 never capillary, sometimes none; style-branches truncate or hairy-append- 

 aged. 



* Disk flmoers perfect, but sterile, the rays fertile. 

 Polymnia. Involucral scales in 2 rows, the 5 outer foliaceous; achenes thick, short, not 



flattened ; pappus none 

 SiLPHirM. Involucral scales thick, imbricated in several rows: achenes flattened, wing- 

 margined, in several tows ; rays In 2 or 3 series ; pappus none or 2 teelh. 

 Parthenibm. Involucral scales short, roundish, in 2 rows: achenes flattened, keeled 

 and margined: rays 5, very short, the heads appearing discoid; pappus of 2 small 

 scales. 

 * * Disk-flowers fertile; rays ileeiihwus except in Hclinpsls, or none. 

 Ecllpta. Rays white, short; involucral scales in 2 rows; receptacle flat; chaff awn- 

 like or bristle-like. 

 Heleopsis. Rays yellow, fertile; achenes 4-angled. 

 Echinacea. Rays rose-colored, pistillate, sterile: achenes 4-sided. 

 Rudbeckia. Rays yellow, neutral: achenes 4-sided, marginless. 

 Lepachys. Rays yellow, neutral: achenes flattened laterally and margined. 

 Helianthos. Receptacle flat or convex : achenes flattish, neither margined nor winged ; 



pappus of 2 deciduous scales or awns. 

 Actinomekis. Receptacle convex ; achenes laterally flattened. 2-awned; leaves decur- 



rent. 

 Coreopsis. Receptacle flat; achenes flat: pappus of 2 short teeth or awns, or a mere 



border, or none. 

 Bidens. Receptacle flat ; achenes flat: pappus of 2-6 awns or teeth which are hispid or 

 barbed-. 

 Tribe Helenieae. Similar to the preceding tribe; receptacle not chaffy; 

 pappus a row of chaffy scales, bristly-dissected in Dysodia; style-branches 

 truncate or with hairy tips. 



Helenidm. Receptacle oblong ; rays 3-5-cleft; involucral scales distinct; leaves decur- 



rent. 

 Dysodia. Receptacle flat; rays few, short; involucral scales united into a cup; ill- 

 scented plants. 

 Tribe Anthcmidece. Rays mostly white or none; involucral scales im- 

 bricated, usually dry and scarious; pappus a short crown or none. Strong- 

 scented herbs with alternate leaves. 



* Receptacle chaffy. 

 Anthemis. Heads large; achenes terete. 

 Achillea. Heads small; achenes flattened. 



