Petrak, Die nordamerikanischen Arten der Gattung Cirsium. 315 
. 
an der Spitze nicht häutig, am Rande sehr klein dornig gewimpert. 
Achaenen größer als jene das C. quercetorum, aber etwas kleiner 
als die das G. remotijolium. 
Sect. Onotrophe. Folia xnembranacea glabrescentia vel saepe 
plus minusve arachnoidaa. Capitula mediocria, raro parva, raris- 
sime majuscula vel magna. Involucri foliola margine integerrima 
vel brevissime spinuloso-aspera, plerumque spinis brevioribus vel 
longioribus terminata. 
Subsect. Crassifolia. Omnino glabrescentia. Capitula sub- 
ebracteata vel ebracteata ovata vel ovato-globosa mediocria. 
Involucri foliola exteriora spinulis 1 — 2 1 / 2 mm longis terminata. 
9. Cirsium Rydbergii. 
Radix mihi ignota. Caulis erectus, certe ad 1 m altus; sul- 
cato-striatus crassiusculus, glaberrimus vel parcissime arach- 
noideo-pilosus, remote foliosus, a medio vel apice 
tantum plus minusve paniculato-ramosus, 
r a m i s 1 — 4 - cephalis valde remote breviter- 
que foliosis vel fere subnudis. Folia radicalia 
utrinque glaberrima, subtus g 1 a u c e s c e n t i a 
ibique interdum imprimis secus nervös parcissime crispule pilosa, 
crassiuscula, in petiolum angustissime alatum remote 
spinoso-dentatum, dentibus ad spinas fere omnino reductis 
paullatim attenuata, ambitu oblongo-lanceolata 
vel lanceolata ad medium vel ad duas t e r - 
tias fere sinuato-pinnatifida, laciniis 1 a - 
tissimis, ambitu ovatis vel triangulari- 
ovatis i r r e g u 1 a r i t e r breviterque dentatis, 
dentibus late t r i a n g u 1 a r i b u s a b r u p t i u s c u 1 e 
acuminatis, spinuloso-ciliatis, spinis sub- 
valid i s stramineis 2 — 6 mm longis terminatis; 
caulina inferiora basi late semiauriculato-semi- 
amplexicauli sessilia, brevissime — vix ad 1 cm 
— decurrentia, alis latis breviter et profunde spinoso 
dentatis, ambitu lanceolatis vel oblongo-lan- 
c e o 1 a t i s , vulgo plus quam ad duas tertias, subremote sinuato- 
pinnatifida, lobis late ovatis vel ovato-rotundatis, inaequaliter 
breviterque dentatis, dentibus late triangularibus abrupte acu- 
minatis, ceterum ut folia radicalia; caulina superiora et suprema 
multo minora, basi late semiauriculato-semiamplexicauli sessilia, 
non vel brevissime decurrentia, ambitu ovata vel oblonga, ab- 
ruptiuscule acuminata, margine remote sinuato-dentata, spinuloso- 
ciliata spinis subvalidis 1 — 3 mm longis terminata. 
Capitula in apice caulis et ramorum breviter pedun- 
culata, ebracteata vel interdum br acteis 
1 — 2 multo minoribus lineari-lanceolatis, 
nt argine pectinato-spinulosis suffulta, basi 
parum excavata vix dilatata, ovata vel ovato-ob- 
longa, cum flosculis 2 l / 2 — 3 x / 4 cm longa, 1V 2 — 2 cm lata. 
