DICOTYLEDONOUS PLANTS. 49 



and among the most specialized for insect fertilization. The 

 genera of the northern United States are divided into 2 sub- 

 orders : I. TubulifloEjE, corolla of the perfect flowers 

 tubular and 6-lobed; II. Liguliflobjs, corollas all strap- 

 shaped and flowers all perfect. 



I. TUBULIFLORJE. 



I. ERIGERON, FLEABANE. 



Heads many-flowered, flat or nearly hemispherical, very 

 many-rayed, the rays narrow, pistillate. Scales of the in- 

 volucre narrow and overlapj)ing but little. Akenes flatfish, 

 crowned with a single row of hair-like bristles (Fig. 110), or 

 sometimes with shorter bristles or scales outside these. Disk 

 yellow, rays white, pinkish, or purple. 



a. (E. ANNUUS), Common Fleabane. Stem grooved and 

 stout, branching, 2-5 ft. high, with scattered hairs, lowest leaves 

 petioled, ovate, coarsely toothed, those higher up the stem suc- 

 cessively narrower, sessile ; heads in a large loose corymb ; rays 

 short, white or purplish. Annual or biennial. 



b. (E. STKiGOSus), D.iiSY Fleabane. Considerably resembling 

 the preceding species, biit with entire leaves, smaller and less 

 branched stem, smaller heads, and longer rays. Annual or biennial. 



c. (E. BELLiDiFOLius), RoBix's Plaxtain. Soft-hairy ; stems 

 sometimes throwing out offsets from the base ; simple, erect, 1-2 

 ft. high ; root-leaves obovate-obtuse, somewhat serrate ; stem-leaves 

 few, lance-oblong, acute, clasping ; heads rather large, 1-9, on long 

 peduncles, with 50-60 long, rather broad, bluish-purple or reddish- 

 purple rays. Perennial. 



(I. (E. Philadelphicus.) Rather hairy ; stems slender, about 2 

 ft. high ; root-leaves spatulate and toothed ; stem-leaves usually 

 entii-e and strongly clasping, sometimes with a heart-shaped or eared 

 base ; heads several, small, long-petioled ; rays exceedingly numer- 

 ous, thread-like, reddish purple or flesh-color. Perennial. 



IL ANTHEMIS, CHAMOMILE, MAYWEED. 



Heads many-flowered, with ray-flowers, rays pistillate or 

 neutral. Involucre of many small, dry, close-pressed scales. 

 Akenes nearly cylindrical, generally ribbed ; barely crowned 



