THISTLE FAMILY 987 



XV. HYDROPHILI. 



Leaves thick, entire or rarely minutely denticulate; inflorescence dense. 



Heads discoid; stem-leaves more or less clasping. 92. S. pacificus. 



Heads radiate; stem-leaves narrowed at the base. 93. S. hydrophilus. 



Leaves dentate; inflorescence open. 94. S. hydrophiloides. 



XVI. CRASSULI. 



Stem-leaves linear or linear-lanceolate. 



Stem naked above; disks 8-10 mm. broad. 95. S. pereziifolius. 



Stem leafy; disks 12-15 mm. broad. 96. S. lapathifolius. 

 Stem-leaves ovate or ovate-lanceolate. 



Leaves firm; bracts very thick and fleshy. 97. S. crassulus. 



Leaves thin; bracts not very thick. 98. S. semiamplexicaulis. 



XVII. RAPIFOLII. 

 One species. 99. 5. rapifolius. 



XVIII. IXTEGERRIMI. 



Heads several. 



Bracts of the involucres narrowly linear-lanceolate, long-attenuate. 

 Bracts without black tips; leaves entire-margined. 



Plant low, 1-3 dm. high, simple, more or less villous. 



100. S. Scribneri. 



Plant tall, 4-10 dm. high, branched, glabrous. 101. S. integerrimus. 



Bracts usually black-tipped; leaves more or less dentate or denticulate. 

 Leaves thick, the basal ones obovate, dentate. 102. S. Hookeri. 



Leaves thin, the basal ones oblanceolate or spatulate, merely denticulate. 



103. S. dispar. 

 Bracts of the involucres linear or oblong, rather abruptly acute, with a lanceolate or 



triangular black tip. 

 Basal leaf-blades cordate to broadly oval, rather abruptly contracted into the 



petioles. 



Rays ochroleucous or white. 104. 5. Leibergii. 



Rays deep yellow. 



Leaves more or less dentate or denticulate; stem 3-10 dm. high. 



105. S. exaltatus. 



Basal leaves entire; stem 2-3 dm. high. 106. S. Flintii. 



Basal leaf-blades spatulate to linear-oblanceolote or rarely lanceolate, gradually 



tapering into the petioles. 

 Bracts about half as long as the fully developed disk. 



Plant 6-8 dm. high; inflorescence open, broad, about 2 dm. wide. 



107. S. lalus. 



Plant 3-6 dm. high, slender; inflorescence 5-8 cm. broad, with a few heads. 



33. S. lugens. 



Bracts more than half as long as the disk; inflorescence usually congested. 

 Leaves crisp, as well as the stem, conspicuously arachnoid-hairy, especially 

 when young; inflorescence dense; heads less than 1 cm. high. 



108. S. condensatus. 

 Leaves not crisp, only slightly villous when young ; inflorescence more open ; 



heads usually over 1 cm. high. 

 Leaves more or less dentate; inflorescence even in age a flat-topped 



corymb. 109. S. columbianus. 



Leaves merely callous-denticulate; inflorescence with a short-peduncled 

 terminal head and the lateral ones usually very long-peduncled. 



110. S. perplexus. 

 Heads solitary. 111. S. solitarius. 



XIX. MEGACEPHALI. 



One species. 112. S. megacephalus 



XX. VULGARES. 



One species. 113. 5. vulgaris. 



XXI. PALUSTRES. 

 One species. 114. S. palustris. 



1. S. accidens Greene. Stem 4-10 dm. high, simple and leafy; basal leaves 

 and lower stem-leaves tapering into rather long winged petioles, lanceolate or 

 oblanceolate, 10-15 cm. long, dentate or denticulate; upper stem-leaves linear- 

 lanceolate, sessile and somewhat clasping; heads few or several on erect branches, 

 nodding; involucre 2-2.5 cm. broad; bracts glabrous, thin, oblong-linear, acute. 

 S. Bigelovii Hallii A. Gray. S. scopulinum Greene. Mountains: Colo. -Utah 

 N.M. Wyo. Mont. Jl-O. 



2. S. chloranthus Greene. Stem 3-10 dm. high, leafy; basal leaves and 

 lower stem-leaves oblanceolate, abruptly contracted into short, winged petioles, 

 coarsely dentate, acute; uppermost leaves sessile, lanceolate; heads several, corym- 

 bose or racemose, the lower ones on elongate, erect peduncles, nodding; invo- 

 lucres openly campanulate, 12-15 mm. high and 20-25 mm. broad; bracts gla- 

 brous, thin, linear, oblong, or lanceolate, acute. S. Bigelovii A. Gray, in part. 



