20 University of California Publications in Botany. [VOL. 3 



Pappus present. 



Kay-flowers maturing achenes: pappus coroniform: leaves ample 

 : 45. WYETHIA, p. 127. 



Bay-flowers not maturing achenes. 



Pappus of 2 slender awns thickened at base and 4 or more 



much shorter erose paleae: peduncles slender 



46. VIGUIERA, p. 128. 



Pappus of 2 acute or awned paleae: peduncles often swollen 



under the head 47. HELIANTHUS, p. 129. 



Disk-achenes flat, compressed, the 2 acute angles either ciliate or winged. 



Achenes not wingejd, but strongly ciliate 48. ENCELIA, p. 133. 



Achenes broadly winged 49. VEKBESINA, p. 137. 



Disk-achenes sterile: ray achenes completely enclosed in their bracts 



52. MELAMPODIUM, p. 144. 



B. Involucral bracts in two very dissimilar series and the outer ones 

 much narrower than the inner ones. 



Leaves mainly radical or alternate, linear to filiform or parted into very 

 narrow lobes 50. COREOPSIS, p. 139. 



Leaves opposite. 



Pappus of barbed awns: heads medium-sized or large 



51. BIDENS, p. 143. 



Pappus paleaceous: heads small: rays white 43. GALINSOGA, p. 126. 



Pappus none: marginal achenes completely enclosed in their bracts ., 



52. MELAMPODIUM, p. 144. 



TRIBE 6. MADIEAE. TARWEED TRIBE. 



Ours annual or biennial herbs (except one species of no 55). 

 Herbage often glandular and viscid or heavy-scented. Leaves, 

 alternate or opposite. Bracts of the involucre in a single series, 

 each partly or completely enclosing an achene. Bracts of the 

 receptacle commonly in a single series between disk and ray and 

 often united into a cup, or sometimes scattered among the disk- 

 flowers. Rays always present in our genera, sometimes incon- 

 spicuous. Anthers not caudate. Ray-achenes always fertile,, 

 seldom pappose ; disk-achenes either fertile or sterile, their pappus 

 paleaceous, awn-like, or none. 



Ray-achenes laterally compressed with narrow back, each completely en- 

 folded by its deeply sulcate involucral bract which is strongly carin- 



ate on the back.... 53. MADIA, p. 145. 



Ray-achenes commonly obcompressed with broad rounded back, each par- 

 tially or wholly enfolded by its involucral bract which is also rounded 

 on the back. 



