Colorado Wekd Seeds 
/D 
Fig. 143. L o n g - 
headed Cone-flower 
(Ratibida column- 
aris). A. Top view. 
B. Edge view, x 12. 
Long-headed or 1’rairie Cone-flower 
(Ratihida columnaris (Sims.) D. Don., 
RatiMda columnifera (Nutt.) Woot. & 
Standi.) (Fig. 143). — Seeds light neutral- 
gray to dark neutral-gray in color, flat- 
tended, a prominent ridge as long as the 
seed on one side, and both sides marked 
with 12-16 fine rounded ridges parallel to 
each other and as long as the seed : seeds 
2-2.5 mm. long, 1-1.5 mm. wide. 
4. Yarrow, Milfoil 
(Achillea (Vaillant) L.) 
Achenes oblong, flattened, distinctly 
margined ; pappus wanting. 
Common Yarrow, Milfoil (Achil- 
lea millefolium L.) (Fig. 144). — Seeds 
pallid neutral-gray to light olive-gray, 
flattened, oblong, margins light, nearly 
white in color ; seeds 1.2-1. 5 mm. long, 
.4-.7 mm. wide. 
Fig. 144. Common Yar- 
row (Achillea millefolium), 
a. Top view. b. Edge view. 
X 30. 
5. Thistle, Common or Plumed Thistle 
(Garduus L., Cirsium (Tourn.) Hill.) 
Achenes oblong, flattened, seldom ribbed, occasionally obscurely 4-angled ; 
pappus of plumose bristles united at the base into a ring, which drops away 
as a cap at maturity. 
Key to Species 
Seeds streaked with flne black lines 1..C. lanceolatus 
Seeds not streaked 
Seeds with a circular, yellow band at the top , 2..C. discolor 
Seeds uniformly brown in color 
Seeds 5-7 mm. long Z . .C. filipenduliis 
Seeds 2.5-3 mm. long 4 . . (7. arvensis 
