72 COMPOSITAE 



polygamo-dioeeious, in cymose clusters, disposed in a long 1 narrow interrupted 

 panicle. Low prairies; May-June; common; Winneshiek and Fayette counties. 

 VALERIAN ELLA Poll. Annual branched herbs, with tufted basal leaves, 

 and terminal capitate, corymbed or panicled flowers. Calyx-limb short and 

 toothed or obsolete. Corolla small, 5-lobed, nearly regular. Stamens 3. 

 Fruit 3-celled, one cell 1-seeded, the others empty. 



V. chenopodifolia (Pursh) DC. Stem glabrous, 1-2 feet high; lower and 

 basal leaves spatulate, obtuse, sometimes repand, the upper oblong or lance- 

 olate, entire, sessile; flowers in dense cymes; corolla white; fruit triangular- 

 pyramidal, glabrous or pubescent. Moist soil; May-July; reported from Lee 

 county by Arthur. 



COMPOSITAE Adans. Thistle Family. 

 Ours herbs, with watery or resinous sap, and opposite alternate or ba- 

 sal exstipulate leaves. Flowers perfect, pistillate or neutral, infrequent- 

 ly monoecious or dioecious, few or many borne on a common receptacle 

 which is subtended by a common involucre composed of few or many bracts 

 arranged in one or more series. Receptacle naked or chaffy, smooth, pit- 

 ted or honeycombed. Calyx-tube adherent to the ovary, the limb wanting 

 or of bristles, teeth, scales, awns, or crown-like or cup-like and is known as 

 the pappus. Corolla tubular, 5-lobed or 5-cleftor the marginal flowers 

 with a strap-shaped or ligulate corolla; the heads are radiate when the ray- 

 flowers are present, discoid when absent, the tubular are the disk'flowers. 

 Stamens usually 5, borne on the corolla and alternate with its lobes, the an- 

 thers united into a tube which sheaths the style, syngenesious, distinct 

 or nearly so in Kuhnia, sometimes appendaged at the apex or sagittate or 

 tailed at the base, the pollen grains globose, rough or echinate. Ovary 1- 

 celled, 1-ovuled; style of the fertile flowers 2-cleft, the branches various and 

 naked or variously appendaged; stigmas marginal; style of sterile flowers 

 usually undivided. Fruit an achene. A large family and well represented 

 in Iowa. Some writers include the two following families with this one. 



Tribe Vcrnonieae. Heads discoid; flowers tubular, perfect, never yellow; 

 style-branches filiform or subulate; leaves alternate or scattered. 

 Vbbnonia. With us the only genus. 

 / Tribe Eupatorieae. Heads discoid; flowers tubular, perfect, never yel- 

 low; style-branches thickened upward, obtuse, minutely pubescent; leaves 

 alternate, opposite or whorled. 



Ecjpatoricm. Aohenes 5-angled; pappus of numerous capillary bristles; involucral 



bracts more than 4. 

 Kuhnh. Achenes 10-ribbed; Involucral bracts striate-nerved; pappus strongly plu- 

 mose. 

 Liatris. Achenes 10-ribbed: involucral bracts faintly striate; pappus plumose or bar- 

 bellate ; heads spicate or racemose. 

 Tribe Astereae. Heads radiate or discoid; style-branches of the perfect 

 flowers flattened, with triangular appendages above; flowers often yellow; 

 anthers not tailed at the base; leaves alternate. 



Grindelta. Heads large; flowers fertile, many; pappus of caducous awns. 

 CHRrsopsis. Heads many-flowered; pappus double, the outer of chaffy scales, the 



inner of capillary bristles. 

 Aplopappus. Heads many-flowered, radiate; pappus persistent, of many unequal 



bristles; achenes white-tomentose. 

 Soiadago. Heads small, radiate, few-many-flowered, yellow, rarely white; pappus of 

 numerous nearly equal capillary bristles. 



