238 American Midland Naturalist Monograph No. 7 



Series 11. liguliflorae DC. 

 1. Pappus none; annual herbs with alternate leaves and yellow flowers; bracts 

 of the involucre about 8. 

 2. Heads numerous; achenes 20-30-nerved; tall paniculately branched 

 herbs with ovate, repand-dentate or lobed leaves 59. Lapsana 



2. Heads few; achenes 8-10-ribbed; low glaucescent herbs with clasping 



entire or lobed leaves 60. Serinia 



1. Pappus present. 



3. Pappas composed of scales, or of scales and bristles, or of short bristles 



only. 

 4. Flowers yellow; pappus double, the outer of short thin scales, the inner 

 of bristles 61. Krigia 



4. Flowers blue (sometimes white or pink) ; pappus a short crown of 



numerous small chafTy scales 62. Cichorium 



3. Pappus consisting wholly of capillary bristles. 



5. Pappus plumose. 



6. Leaves grass-like 65. Tragopogon 



6. Leaves not grass-like. 



7. Plants scapose 63. Hypochaeris 



7. Plants leafy-stemmed 64. Picris 



5. Pappus not plumose. 



8. Heads usually several on each stem; leaves not all basal. 



9. Achenes more or less flattened; leaves usually lobed and often 

 somewhat soft-prickly. 

 10. Achenes filiform-beaked, or if merely narrowed at the apex, 



the flowers not yellow 66. Lactuca 



10. Achenes truncate at the apex, not beaked; flowers yellow, 50 



or more in each head 67. Sonchus 



9. Achenes cylindric or prismatic. 



1 1 . Flowers whitish or purplish; heads pendent 68. Prenanthes 



11. Flowers yellow; heads erect. 



12. Achenes beakless. 



13. Leaves entire or merely toothed 69. Hieracimn 



13. Leaves lobed 70. Crepis 



12. Achenes filiform-beaked 71. Pyrrhopappus 



8. Heads solitary; leaves all basal; flowers yellow. 



14. Achenes not muricate, 10-nerved; leaves (in our species )entire 



..72. Agoseris 



14. Achenes not muricate near the apex, 4- to 5-nerved; leaves 



lobed 73. Taraxacum 



Tribe 1. Ambrosieae 



1. Iva L. — Marsh-elder 



1. Heads in bracted spikes; stem hispid; fields and loadsides, chiefly 

 in the s. half of 111. Aug.-Oct /. ciliata Willd. 



1. Heads spicate-paniculate; stem glabrous, or pilosulous above; 

 roadsides, railroad yards, waste places, chiefly in the n. half of 

 111. July-Sept /. xanthijolia Nutt. 



2. Ambrosia L. — Ragweed 



1. Leaves pinnatifid or bipinnatifid. 



2. Leaves petioled, bipinnatifid; fruit with 5-7 sharp tubercles; 



