354 IOWA ACADEMY OF SCIENCE 



and abruptly truncate at the apex; base long- attenuate; differs 

 from Tussilago Farfara in being smaller and broader towards 

 the apex rather than towards the base. 0., quite common in 

 waste places. Introduced from Europe. 



103. Arctium- minus Behr. Burdock. L., 4 — 6 mm. W., 1.8 — 2.8 

 mm. C, dark brown spotted or mottled with black; with fine 

 longitudinal dark lines. S., straight or curved; somewhat ob- 

 long; tapering at the base; with a few narrow longitudinal 

 ridges. 0., not truly pernicious but common. Introduced from 

 Europe. 



104. Cirsium lanceolatum L. Hill. Common or Bull Thistle. 

 L., 3. — 4.2 mm. AY.. 1.2 — 2. mm. C, light straw-colored flecked 

 with blackish markings. S., smooth, slightly flattened, obovate; 

 apex set at an angle to the longitudinal axis, cup-shaped with in- 

 curving sides ; base rather abruptly contracted. 0., common in red 

 clover, alfalfa and grass seeds. Naturalized from Europe. 



105. Cirsium ar reuse L. Scop. Canada Thistle. L., 2.2 — 3.4 

 mm. W., .8 — 1.2 mm. C, rich golden brown. S., obovoid and 

 slightly flattened, apex truncate and cup-shaped with incurving 

 edges. 0., found in clover seed. Naturalized from Europe. 



106. Centaurea Cyanus L. Blue Bottle, Bachelor's Button. 

 Corn Flower. L., 3.2 — 4.8 mm. W., 1.8—2.2 mm. 0., shining 

 white or yellowish gray, sometimes bluish white. S., flattened 

 cylindrical except that the base is obliquely truncate; apex 

 abruptly and squarely truncate with a tubercle in the middle ; 

 pappus bristles quite persistent, 0., common in coarse clover and 

 grass seeds. Appeared in Ithaca, New York, in 1885 and is grow- 

 ing more and more abundant each year. Introduced from Europe. 



107. Cichorium Intybus L. Common Chicory. Blue Sailors. 

 L., 2.5 — 3.5 mm. W., .8 — 1.2 mm. C. light yellowish brown, 

 slightly mottled with black. S., irregularly truncate ; four or five- 

 angled with two to four faint longitudinal lines on each side ; sur- 

 mounted by a double row of scales or bristles. 0., found in 

 clover, alfalfa and grass. Introduced from Europe. 



108. Tragopogan porrifolius L. Salsify. L., 10 — 18 mm. 

 without pappus and 70-80 mm. with pappus. W., 1.8 — 2.3 mm. C, 

 brownish gray flecked with small whitish scales. S., nearly cylin- 

 drical but quite spindle-shaped ; tapering and curving at the 



