PIPER—FLORA OF THE STATE OF WASHINGTON. 609 
SILYBUM. 
1. Silybum marianum (L.) Gaertn. Fruct. & Sem. 2: 378. 1802. MILK THISTLE. 
Carduus mariana L. Sp. Pl. 2: 823. 1753. 
Type coca.ity: “In Angliae, Galliae, Italiae aggeribus ruderatis.”’ 
SPECIMENS EXAMINED: Pullman, Piper in 1902; Vancouver, Piper in 1904. 
CARDUUS. TuisT-e.: 
Dioecious; heads small; perennial by spreading roots ...........-.-- 1. C. arvensis. 
Hermaphrodite; heads larger; biennials. 
Bracts of the involucre all with dilated fringed tips. .........-.- 2. C. americanus. 
Bracts of the involucre or some of them with spiny tips. 
Outer and inner bracts all with spiny tips.........-........ 3. @. lanceolatus. 
Outer bracts spine-tipped; inner ones unarmed. 
Involucre loose, the outer bracts nearly or quite as long 
as the inner. 
Heads clustered, short-peduncled; flowers pink..... 4. C. edulis. 
Heads few, long-peduncled; flowers cream-color.... 5. C. remotifolius. 
Involucre close, the outer bracts much shorter than the 
inner. 
Heads clustered, subsessile, leafy; bracts herbaceous, 
not glandular on the back ................-.--- 6. C. foliosus. 
Heads not clustered, peduncled; bracts coriaceous, 
glandular on the back. 
Outer bracts with spines nearly as long... .--- - 7. C. ochrocentrus. 
Outer bracts with much shorter spines. 
Leaves canescent on both sides; flowers 
usually pink. .........-.-.----------- 8. C. undulatus. 
Leaves green above; flowers whitish... . -- 9. C. palousensis. 
1. Carduus arvensis (L.) Robs. Brit. Fl. 163. 1777. CANADA THISTLE. 
Serratula arvensis L. Sp. Pl. 2: 820. 1753. 
Cnicus arvensis Hoffm. Deutschl. Fl. ed. 2. 17: 130. 1804. 
Cirsium arvense Scop. Fl. Carn. ed. 2. 2: 126. 1772. 
Type LocaLity: European. 
SPECIMENS EXAMINED: Pullman, Piper, July 1, 1895; Tacoma, Piper. 
The Canada thistle is now well established in various places in Washington, but it pro- 
duces good seed only exceptionally, and therefore its spread is slow. 
2. Carduus americanus (A. Gray) Rydberg, Bull. Torr. Club 28: 508. 1901. 
Cnicus carlinoides americanus A. Gray, Proc. Am. Acad. 10: 48. 1874. 
Cnicus americanus A. Gray, Proc. Am. Acad. 19: 56. 1883. 
Type Locauity: “ Rocky Mountains of Colorado.” 
Rance: Washington to California and New Mexico. 
SPECIMENS EXAMINED: Seattle, Piper in 1888; Goose Lake, F'lett 1097. 
3. Carduus lanceolatus L. Sp. Pl. 2: 821. 1753. BULL THISTLE. 
Cnicus lanceolatus Willd. Prod. Fl. Berol. 259. 1787. 
Cirsium lanceolatum Scop. FI. Carn. ed. 2. 2: 130. 1772. 
Type LocaLity: European. 
SPECIMENS EXAMINED: Pullman, Piper, August, 1897; abundant in western Washington. 
4. Carduus edulis (Nutt.) Greene, Proc. Acad. Phila. 1892: 362. 1893. 
Cirsium edule Nutt. Trans. Am. Phil. Soc. 7: 420. 1841. 
Cnicus edulis A. Gray Proc. Am. Acad. 10: 47. 1874. 
Type Loca.ity: ‘The plains of Oregon and the Blue Mountains”? Collected by Nuttall. 
29418—06 mM——-39 
