386 ASTERACEAE. 



38. CENTROMADIA Greene. 



Rigid corymbosely or diffusely branching annuals, 

 with alternate pinnatifid or entire spinescent leaves. 

 Herbage more or less resiniferous or glandular through- 

 out. Involucral bracts subulate, pungent, half enclosing 

 the ray-achenes, persistent. Ray-flowers 15-40, yellow, 

 small, fertile. Disk-flowers sterile. Receptacle convex, 

 chafty throughout, the chafif distinct and persistent. 

 Achenes triangular, the inner angles terminated by a 

 short apiculation, nearly smooth or faintly rugose-tuber- 

 culate. Pappus none. 



1. C. pungens (H. & A.) Greene. Stout with rather rigid 

 ascending or spreading branches, 4-8 dm. high, hirsute or hispid, 

 scarcely viscid, nearly or quite scentless; lower leaves 2-pinnatifid, 

 the upper 1-pinnatifid, the lobes pungent-tipped; chaff of receptacle 

 rigid-pungent; disk-achenes destitute of pappus; ray-achenes nearly 

 black, about 2 mm. long, the ventral angle carinate, the plane sides 

 and rounded back faintly tuberculate-rugose. 



Common in the plains in heavy, rather moist soil. July-Novem- 

 ber. 



2. C. parryi Greene. Widely branching, 3-6 dm. high, sparsely 

 hirsute, minutely resinous-glandular, aromatic; lowest leaves pin- 

 natifid, the cauline linear, entire, sharply pungent, spreading, the 

 uppermost pilose-ciliate toward the base; heads scattered; ray- 

 achenes dull black, 1.5 mm. long, somewhat compressed, smooth 

 on the sides, with a few coarse tuberculations on the back; disk- 

 achenes with 3 or more palese exceeding the corollas; chaff of the 

 receptacle not pungent. 



brackish flats toward the coast. June-August. 



39. DEINANDRA Greene. 



Erect, rigid and brittle, balsamic-viscid annuals, with 

 mostly small few-flowered panicled heads, and entire or 

 serrate leaves. Involucral bracts few, half enclosing 

 their achenes, their tips short, rigid and erect. Rays 

 usually 5, broad, 3-toothed, diurnal. Receptacle chaff}'' 

 only next the rays. Ray-achenes gibbous, tuberculate- 

 rugose, the terminal areola raivsed upon a distinct curved 

 beak from the angle of the ventral face of the achene; 

 disk-achenes mostly sterile, with or without a paleaceous 

 crown. 



Heads subsessile, usually fasciculate-clustered. 1. D.fasciculata. 



Heads solitary, terminating the filiform branchlets. 



Pappus of the disk-flowers not united. 2. D. wrightii. 



Pappus of the disk-flowers united to near the 

 summit. 3. D. kelloggii. 



