234 COMPOS IT ACE AE (COMPOSITE FAMILY) 



Style unbranched or the branches appendaged. Pappus none or chaff or 

 stiff bristles or capillary bristles, simple or plumose 



A. Involucre bracts hooked at tip; leaves not spiny. ARCTIUM (p. 234) 



AA. Involucre bracts not hooked at tip. 

 B. Leaves not spiny. 



C. Pappus at least partly of plumose bristles. 



D. Leaves entire or dentate; heads 1-3 cm. wide. W. C. E. (Honor of H. B. 

 de Saussure, a Swiss botanist.) Saussurea americana (SAW-WORT) 



DD. Leaves pinnatifid; heads 5-10 cm. wide. W. Heads edible. (Gk. kyon = 

 a dog; the involucre spines suggest dog-teeth.) Cynaria scolymus (ARTICHOKE) 

 CC. Pappus none or of simple bristles or scales. CENTAUREA (p. 235) 



BB. Leaves somewhat spiny and often also the involucre. 

 E. Pappus distinctly plumose. 



F. Heads 1-5 cm. wide; involucre bracts not fleshy; akenes not ribbed. 



CARDUUS (p. 234) 



FF. Heads 5-10 cm. wide; involucre bracts fleshy; akenes slightly ribbed. (See 

 DD.) Cynaria scolymus (ARTICHOKE) 



EE. Pappus none to barbellate or fimbriate. 



G. Heads 6-7 cm. wide; leaves green and blotched with white. W. E. (Gk. 

 silybos = the name of a thistle with edible stem.) 



Silybum marianum (LADY'S THISTLE) 

 GG. Heads 2-4 cm. wide; leaves not white-blotched. 



H. Heads not subtended by bristly leaves. CENTAUREA (p. 235) 



HH. Heads subtended by bristly leaves, sessile. U. E. (Gk. kniso = to prick.) 



Cnicus benedictus (BLESSED THISTLE) 



ARCTIUM (BURDOCK) 



Tall, coarse. Leaves broadly ovate, cordate at base, 2-5 dm. long. 

 Heads clustered; receptacle densely bristly. Pappus-bristles short, many, 

 rough, deciduous, in i whorl. (Gk. arktos = a bear ; from the rough 

 involucre.) 



A. Heads racemose, 1.5-3 cm. wide. W. A. minus (COMMON BURDOCK) 



AA. Heads corymbose, 2-5 cm. wide. W. A. lappa (GREAT BURDOCK) 



CARDUUS (THISTLE) 



Stout, erect. Heads rayless, all alike (or dioecious in C. arvensis}. Re- 

 ceptacle flat, densely bristly. Flowers white or red or rarely yellowish. 

 Pappus bristles many, long, in i whorl, united into a ring at base. (The 

 Latin name; said to be from Celtic ard a sharp point.) 



A. Perennial by spreading horizontal rootstocks; heads 15-25 mm. high, dioecious. 

 W. E. One of our worst weeds in cultivated fields. C. arvensis (CANADA THISTLE) 

 AA. Biennial; heads larger, all alike. 



B. None of the involucre bracts spine-tipped, all with dilated fringed tips. W. E. 



C. americanus 



BB. Outer involucre bracts spine-tipped, inner ones not. 

 C. Involucre bracts not at all glandular on the back. 



D. Involucre bracts either nearly equal or some with spreading herbaceous tips. 

 E. Flowers cream-colored. W. C. E. C. remotifolius 



