Tarweed Tribe 419 



opposite. Involucral bracts in 1 series, each partly or 

 wholly enclosing an achene. Bracts of the receptacle 

 commonly in a single series between ray- and disk- 

 flowers. Rays always present and fertile, destitute of 

 pappus. Disk-flowers sterile or fertile, their pappus 

 paleaceous, awn-like or none. 



Ray-achenes laterally compressed, completely enfolded by the involucral 



bract. 

 Rays inconspicuous. 



Disk-flowers several. 35. MADIA. 



Disk-flowers 1-4. 40. HABPAECARPUS. 



Rays showy. 36. MADABIA. 



Ray-achenes somewhat obcompressed, half enclosed by the bracts. 



Leaves spiny ; flowers yellow. 37. CENTBOMADIA. 



Leaves not spiny. 



Herbage somewhat glandular; flowers yellow. 38. DEINANDRA. 

 Herbage not glandular; flowers white or rose color. 



39. CALYCADENIA. 



Ray-achenes obcompressed or clavate, completely enfolded by their bracts. 

 Bracts 5; herbage canescent. 41. LAGOPHYLLA. 



Bracts more than 5. 



Rays showy, yellow or white. 42. BLEPHARIPAPPDS. 



Rays inconspicuous; pappus becoming showy. 43. ACHYRACHAENA. 



35. MADIA Mol. TARWEED. 



Glandular and viscid heavy-scented herbs with at 

 least the upper leaves alternate entire or toothed. Heads 

 axillary and terminal. Involucre angled by the salient 

 carinate backs of the uniserial involucral bracts, these 

 usually completely enclosing the ray-achenes, their tips 

 herbaceous. Receptacle flat or convex, bearing a single 

 series of chaff united and forming a cup between the 

 ray- and disk-flowers, the inner portion naked or fimbril- 

 late. Ray-flowers yellow, rather short, 3-lobed, fertile. 

 Disk-flowers sterile. Pappus none. Achenes laterally 

 compressed, smooth, beakless. 



1. M. sativa Mol. Stem simple with a few short ascending 

 "branches above, erect, stout, 3-9 dm. high, pubescent with slen- 

 der hairs and beset with stalked very viscid glands ; leaves lance- 

 olate, nearly entire, glandular-pubescent; heads 12 mm. high, 



