COMPOSITAE. 261 



beneath, 5-15 cm. long; prickles few; heads large, on nearly naked long 

 peduncles; involucre hemispheric; the bracts firm, closely imbricated 

 in several successively shorter ranks; all prickly pointed and bearing 

 an oblong or linear glandular spot near the tip; flowers yellowish- white; 

 corolla-lobes shorter than the throat. Common on the prairies. 



388. CHAENACTIS. 



Annual, biennial or perennial herbs; leaves alternate, 1-3- 

 pinnately dissected; heads medium or large, peduncled, terminat- 

 ing the branches ; ray-flowers none ; flowers yellow, white or flesh 

 colored, all perfect and tubular but an outer series more or less 

 enlarged simulating rays; involucre campanulate or hemispher- 

 ical; bracts equal, in 1-2 rows; pappus of 4-12 awnless and nearly 

 or quite nerveless hyaline or chaffy scales ; akenes slender, linear, 

 tapering to the base, more or less 4-angled. 



Chaenactis douglasii (Hook.) H. & A. Perennial, loosely white-tomentose 

 throughout, erect, 30-50 cm. high, branched above; leaves oblong-lanceolate 

 in outline, S-10 cm. long, bipinnately parted into numerous rather crowded 

 obtuse segments; heads corymbed; involucre viscid-pubescent, 10-12 mm. high; 

 bracts linear, obtuse; flowers all alike, cream-colored or pinkish; akenes pu- 

 bescent, those of the outer flowers often glandular; pappus of 8-12 large obtuse 

 silvery scales, two-thirds as long as the akenes or in the outer flowers only 

 one-third as long. Gravelly soil. 



389. MATRICARIA. 



Herbs; verj' similar to Chrysanthemum but ray-flowers none 

 (in ours) ; involucre hemispherical or flatter, of numerous more 

 or less scarious appressed scales, in few rows; receptacle high- 

 conical or ovate; pappus none or a minute crown. 



Matricaria matricarioides (Less.) Porter. Annual, 5-20 cm. high, simple 

 or branched, sparsely pubescent or glabrous; leaves oblong, 1-3 cm. long, 

 once or twice pinnately dissected into small linear acute segments; heads 5-9 

 mm. high, terminating short stout peduncles; involucre saucer-shaped, the 

 scales oblong, obtuse, green, with scarious margins; ray-flowers none; disk- 

 flowers yellowish-green; receptacle conical; akenes oblong; pappus represented 

 by a low sometimes 1-2-toothed crown. Dry ground, very common. 



390. RUDBECKIA. 



Mostly perennial herbs; leaves alternate; heads many-flowered, 

 mostly with sterile ray-flowers but rayless in ours; disk-flowers 

 perfect; receptacle elongated, becoming columnar; pappus a 

 chaff-like cup or 4 chaffy teeth more or less united into a cup; 

 akenes quadrangular and mostly laterally compressed. 



Rudbeckia occidentalis Nutt. Stems erect, 50-100 cm. tall, smooth; 

 leaves ovate, acuminate, coarsely dentate or nearly entire, short-petioled or 

 the upper sessile, usually pubescent beneath, smooth above, 6-12 cm. long; 

 heads rayless; disk at length ovate-conical or columnar, 3-5 cm. long, dark- 

 brown; involucre loose, foliaceous; akenes 3 mm. long; pappus merely a low 

 scarious rim on the apex of the akene. Moist open places, in the mountains. 



