THISTLE FAMILY 987 



XV. Hydropiiilt. 



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. CUASSULl. 



Stem-leaves linear or linear-lanceolate. 



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



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

 Stem-leaves ovate or ovate-lanceolate. 



Leaves firm; bracts very thick and fleshy. 07. S. crassulus. 



Leaves thin; bracts not very thick. 98. S. semi ample xicauUs, 



99. S. rapifolius. 



XVII. Rapifolii. 

 One species. 



XVIIl. INTEGERRIMI. 



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. Ilookeri. 



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



10;5. 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. c t u - 



Rays ochroleucous or white. 104. ^. Leibergti, 



Rays deep yellow. 



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



105. S. exaltatus. 



Basal leaves entke: stem 2-3 dm, high. 106. S. FUntii. 



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. 5. latus. 



Plant 3-6 dm. high, slender; inflorescence 5-S 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 voune; inflorescence dense; heads less than 1 cm. high. 



-^^ ^' 108. S. condensatus. 



Leaves not crisp, only slightly villous when young; inflorascence 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 merelv callous-denticulate; inflorescence with a short- peduncle d 

 terminal head and the lateral ones usually ver>' long-peduncled. 



110. 5. per plexus. 



Heads solitary. 

 One species. 

 One species. 

 One species. 



XIX. Megacephalt. 



XX. VULGARES. 



XXI. Palustkes. 



111. S. solitarius. 



112. S. megacephalus 



113. S, vulgaris. 



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 hnear- 

 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. Mountams: Colo.— L tab 

 — N.M. — Wyo. MonL 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, 



heads 



mm. high 



b™, E, linear: oblong,' or lanceolate, acute. S. Bigelovii A. Gray, in part. 



