COMPOSITAE - - THISTLE FAMILY BULL THISTLE 801 



Cirsium canescens Nutt. Woolly Thistle 



Branching perennial 2-4 feet high, woolly throughout bearing single medium 

 sized heads, stem angled, white woolly; leaves, radical 8 inches to 1 foot long, 

 the divisions usually 2-lobed, prominently ribbed, ending in stout spines; stem 

 leaves except the lower, 1-4 inches long, pinnatifid, the upper sessile, slightly 

 roughened, with a slight cottony down, the lower white, woolly; heads \ l / 2 to 

 2 inches high, bracts of the involucre somewhat arachnoid, lower scales with a 

 broad base, glutinous ridge, and ending in minutely serrated spine, inner scales 

 long, attenuated, tips straw colored; flowers purple. This is Carduus Flod- 

 mannii Rydb. 



Distribution. This species is distributed from Mason City, Iowa, to south- 

 western Minnesota, west to the Rocky Mountains. Collected by Charles A. 

 Geyer in 1839, and described by Nuttall. The writer has seen it very abundant 

 in Wyoming, Montana and Colorado. 



Cirsiuin discolor (Muhl.) Spreng. Prairie Thistle 



Tall, branching, leafy biennial, 5-7 feet high, with heads larger than the 

 Canada thistle; stem striate, slightly hirsute; leaves radical 12-14 inches long, 

 deeply pinnatifid, the divisions frequently divided, prickly toothed, the upper 

 surface smoothish, and the lower white, woolly single heads terminating the 

 branches, with purple flowers, heads \ l /> inches high; bracts of the globose 

 involucre slightly arachnoid, lower bracts ovate, with a broad base and a weak 

 prickly recurved bristle, slight dorsal gland, inner linear lanceolate with a nearly 

 colorless entire appendage ; flower purple ; lobes of the corolla terminating in 

 clavate tips, anther tips acute, filaments pubescent ; bristle of pappus plumose ; 

 achenium smooth, upper part yellow. 



Distribution. In fields and along roadsides from Quebec, Ontario, south 

 through New England, New York and Georgia, west to Missouri, Nebraska 

 and South Dakota. 



Cirsiuin ochrocentrum Gray 



Biennial, 2-8 feet high ; white tomentum ; leaves commonly deeply pinnatifid 

 and armed with long yellowish prickles; heads 1-2 inches high; involucral 

 scales with a viscid line on the back, with a prominent spreading yellowish 

 prickle ; corolla purple, rarely white. 



Distribution. From Arizona to Colorado and Utah. 



Cirsiuin undulatum (Nutt.) Spreng. 



Biennial 1-2 feet high, white tomentose ; leaves pinnately parted, some- 

 what prickly; heads about 2 inches high; the outer bracts thickened by gland- 

 ular-viscid ridge ; corolla rose-color, purple or pale purple ; the variety mega- 

 cephaleuin with larger heads. 



Distribution. West of the Missouri River to Oregon and New Mexico. 



Injurious properties. None of the species is poisonous so far as the 

 writer knows. The spiny involucre and spiny leaves inflict inflammation and 

 cause the formation of pus. 



28. Centaur ea L. 



Perennial or annual herbs, with leaves alternate, entire, dentate, incised or 

 pinnatifid ; involucre ovoid or globose ; bracts in many series ; marginal flowers 

 usually neutral and larger than the central ones in some species; all the flowers 

 perfect and, fertile ; heads middle-sized, tubular, purple-violet, or white or rarely 



