270 Petrak, Die nordamerikanischen Arten der Gattung Cirsium. 
ebracteata vel parum bracteata. Involucri parce 
arachnoidei vel fere glabrescentis foliola exteriora et media e basi 
ovato-oblonga abruptiuscule attenuata, a medio circiter 
erecto-vel plus minusve recurvo-patentia, 
rigida, in spinas subvalidas vel validas 
excurrentia, m argine integerrima vel bre- 
vissime spinuloso-hirsuta, interiora et intima 
vulgo multo longiora, recta, appressa, linearia vel lineari-lanceolata, 
elongato-acuminata, dorso saepe plus minusve purpurascentia. 
1. Arizonica. 
Capitula s u b e b r a c t e a t a vel fere ebrac- 
teata, ovato-oblonga vel ovata, mediocria 
vel majuscula. Involucri foliola exteriora et media dorso 
apicem versus saepe parum viscido-carinata, spinis 
subvalidis terminata, interiora et intima multo longiora, apicem 
versus plus minusve purpurascentia. Corollae limbus 
vel ad duas tertias vel ad basin fere aequa- 
liter q u i n q u e f i d u s , a tubo vix distinctus 
eoque parum longior. 
1. Cirsium arizonicum. Caulis elatus ramosus, ramis plus 
minusve elongatis, breviter foliosis monocephalis. F o 1 i a ut- 
rinque plus minusve arachnoideo-tomentosa, 
supra canescentia subtus albida. 
2. Pulchella. 
Capitula bracteata, ovato-oblonga vel 
oblongo-cylindrica, raro ovata mediocria. 
Involucri foliola exteriora et media dorso non viscido- 
carinata, spinis validis, interdum ad 2 cm longis, raro sub- 
validis brevioribus, erecto-patentibus terminata, interiora et intima 
multo vel parum longiora, linearia, elongato-acuminata, appressa, 
interdum plus minusve purpurascentia. Corollae limbus 
ad duas tertias vel ad basin fere subregula- 
riter quinquefidus eoque subduplo, inter- 
dum fere triplo longior. 
1. Cirsium Rothrockii. Folia utrinque glaberrima, 
subtus plus minusve glaucescentia subrigida, 
late sed breviter decurrentia. Capitula oblongo-ovata 
vel ovata. Involucri foliola exteriora et media spinis sub- 
validis erecto-vel plus minusve recurvo-patentibus terminata. 
Corollae purpureae limbus ad duas tertias vel ad 
b a s i n fere inaequaliter vel subregulariter quinquefidus eoque 
subduplo longior. 
2. Cirsium pulchellum. Folia utrinque glabrescentia 
vel saepe imprimis subtus arachnoidea non 
vel breviter decurrentia. Capitula oblonga vel ob- 
longo-cylindrica. Involucri foliola exteriora et media 
spinis subvalidis vel validis terminata. Corollae purpureae limbus 
