1	"Adaxial leaf face with slender appressed bristle-like prickles"	"Cirsium vulgare"
1	"Adaxial leaf face without prickles"	2
2	"Plants dioecious or nearly so"	"Cirsium arvense"
2	"Plants with bisexual flowers"	3
3	"Corolla lobes 1--2+ × tube"	4
3	"Corolla lobes < tube"	8
4	"Corolla pink-purple to red-purple, red-pink, or red; heads generally erect; leaf adaxially tomentose (occasionally +- glabrous in age)"	5
4	"Corolla white to pink or lavender; heads generally nodding; leaf adaxially densely velvety, with short, erect, jointed hairs, also cobwebby --- serpentine wetlands; SnFrB, SCoRO"	6
5	"Corolla bright red or +- red-pink; corolla throat 2--5 mm, lobes 13--18 mm; SNH, W&I"	"Cirsium arizonicum var. arizonicum"
5	"Corolla pink- to +- red-purple; corolla throat 5--8 mm, lobes 10--14 mm; e DMtns"	"Cirsium arizonicum var. tenuisectum"
6	"Fruit 4.1--5 mm; phyllary spines 1--2 mm"	"Cirsium fontinale var. fontinale"
6	"Fruit 3.4--4.1 mm; phyllary spines generally 2--6 mm"	7
7	"Longer spines of cauline leaves 10--18 mm; most phyllaries without marginal spines"	"Cirsium fontinale var. campylon"
7	"Longer spines of cauline leaves 4--7 mm; many outer phyllaries with marginal spines"	"Cirsium fontinale var. obispoense"
8	"Abaxial face of outer and middle phyllaries with long, sticky-resinous ridge (milky when fresh, dark when dry, occasionally very narrow), occasionally poorly developed or 0 in <i>Cirsium mohavense</i>"	9
8	"Abaxial face of outer and middle phyllaries without sticky-resinous ridge"	23
9	"Margins of phyllaries minutely spiny-fringed"	10
9	"Margins of phyllaries entire"	11
10	"Heads generally 2.5--3 cm; fruit +- 5 mm, oblong, tapered near base; tidal marshes; deltaic GV (Suisun Marsh, Solano Co.)"	"Cirsium hydrophilum var. hydrophilum"
10	"Heads generally 3--3.5 cm; fruit 4--5 mm, oblong or elliptic; serpentine springs; n SnFrB (Mount Tamalpais, Marin Co.)"	"Cirsium hydrophilum var. vaseyi"
11	"Stem evidently coarse-hairy with multicellular hairs, also cobwebby to densely tomentose with long, fine hairs; cauline leaves generally +- clasping, with expanded basal lobes; leaf veins generally prominently raised abaxially"	12
11	"Stem with few or 0 coarse, multicellular hairs, thinly to densely cobwebby or tomentose with long fine hairs; cauline leaves generally not clasping with expanded basal lobes; leaf veins generally not prominently raised abaxially"	13
12	"Larger heads 15--25 mm diam; outer phyllaries generally << inner, sticky-resinous ridge prominent, well developed, appearing dark brown on dry specimens"	"Cirsium cymosum var. canovirens"
12	"Larger heads 20--35 mm diam; outer phyllaries long, often nearly = inner, sticky-resinous ridge weakly developed"	"Cirsium cymosum var. cymosum"
13	"Involucre 2.5--4.5 cm"	14
13	"Involucre 1.5--2.5(3) cm"	16
14	"Mid and distal leaves not or scarcely decurrent"	"Cirsium undulatum"
14	"Mid and distal leaves evidently decurrent as spiny wings to 5 cm"	15
15	"Phyllary spines generally 2--4 mm; corolla +- white"	"Cirsium canescens"
15	"Phyllary spines generally 5--12 mm; corolla white to pale lavender or pink"	"Cirsium ochrocentrum var. ochrocentrum"
16	"Rosette arising from runner roots; leaf adaxially green, thinly gray-tomentose --- n KR"	"Cirsium ciliolatum"
16	"Rosette arising from taproot or woody caudex; leaf adaxially gray-tomentose or becoming +- green"	17
17	"Phyllaries +- loosely appressed, generally ascending to spreading above appressed base"	18
17	"Phyllaries tightly appressed, only tip-spines spreading"	20
18	"Phyllary tip-spine generally 1--3 mm; SCoR and c SNF to mtns of SW"	"Cirsium occidentale var. californicum"
18	"Phyllary tip-spine generally 3--10 mm"	19
19	"Involucre, including phyllary tips generally ovoid to +- spheric; tip-spines of phyllaries generally 3--7 mm; outer phyllaries generally spreading or ascending --- SNH, GB"	"Cirsium inamoenum var. inamoenum"
19	"Involucre, including phyllary tips often wider than long; tip-spines of phyllaries generally 5--10 mm; outer phyllaries often reflexed"	"Cirsium neomexicanum"
20	"Corolla +- white to pink or pale lavender; involucre pale green or straw-colored"	21
20	"Corolla generally +- dark rose-purple (white); involucre generally dark green or +- purple --- n CA-FP, MP"	22
21	"Distal leaves generally conspicuously decurrent as spiny wings; wet soils, streams, springs; SNE, DMoj"	"Cirsium mohavense"
21	"Distal leaves not or only weakly decurrent; dry sites; SCoR and c SNF to mtns of SW"	"Cirsium occidentale var. californicum"
22	"Larger spines of distal cauline leaves generally <= 7 mm"	"Cirsium douglasii var. breweri"
22	"Larger spines of distal cauline leaves generally 7--20 mm"	"Cirsium douglasii var. douglasii"
23	"Margins of outer phyllaries irregularly toothed to spiny-ciliate"	24
23	"Margins of outer phyllaries +- entire"	30
24	"Leaves densely gray- or white-felty-tomentose on faces --- coastal dunes, headlands; s CCo"	"Cirsium rhothophilum"
24	"Leaves adaxially green and glabrous to +- gray-hairy with multicellular hairs and/or finely cobwebby, abaxially sometimes densely gray- or white-tomentose"	25
25	"Corolla 30--45 mm, +- bright rose-purple"	"Cirsium andersonii"
25	"Corolla 17--28 mm, white or cream to purple"	26
26	"Heads generally not closely subtended by well-developed distal leaves or clustered leafy bracts; phyllary tips flattened, generally ascending, connected side-to-side by cobwebby hairs or not"	27
26	"Heads generally closely subtended by +- well-developed distal leaves or clustered bract-like leaves; phyllary tips needle-like, ascending to radially spreading, connected side-to-side by long, cobwebby, or stouter, multicellular hairs"	29
27	"Plant stout, generally 10--30 dm; stem 2--10 cm diam near base, evidently hollow; middle and inner phyllaries entire --- SnJV"	"Cirsium crassicaule"
27	"Plant slender, generally 1--11 dm; stems generally < 2 cm diam near base; middle and inner phyllaries irregularly toothed or spiny-ciliate"	28
28	"Phyllary margins irregularly toothed or cut"	"Cirsium remotifolium var. odontolepis"
28	"Phyllary margins ciliate with minute spreading to recurved spines"	"Cirsium remotifolium var. rivulare"
29	"Corolla lobes linear, tips not knob-like; style conspicuously exserted; stem cobwebby, +- glabrous in age, coarser, multicellular hairs 0"	"Cirsium andrewsii"
29	"Corolla lobes thread-like, tips knob-like; style included or exserted 1--2 mm; stem evidently hairy with +- coarse multicellular hairs, often cobwebby to densely tomentose with long, fine hairs"	"Cirsium brevistylum"
30	"Outer and middle phyllaries lance-linear to ovate, appressed; tip-spines 1--12 mm, generally ascending to erect"	31
30	"Outer and middle phyllaries with short-appressed bases and lanceolate to linear or needle-like, ascending to stiffly spreading tips; tip-spines generally 1--35 mm"	40
31	"Plant erect; stem openly branched distally --- biennial; dry sites; SCoR and c SNF to mtns of SW"	"Cirsium occidentale var. californicum"
31	"Plant generally +- compact, stemless or low-growing and branched +- throughout (if erect, generally distally unbranched)"	32
32	"Perennial herb from runner roots; generally from dry sites; NCo, NCoRO, CW"	"Cirsium quercetorum"
32	"Biennial or perennial herb that flowers once, then dies, taprooted; generally from moist sites; widespread"	33
33	"Corolla pink to purple; SNH, SnBr, SNE"	"Cirsium scariosum var. congdonii"
33	"Corolla white or faintly pink- or lilac-tinged"	34
34	"Abaxial leaf face generally gray-tomentose; CaRH, SNH, Wrn"	"Cirsium scariosum var. americanum"
34	"Abaxial leaf face generally +- glabrous (occasionally tomentose in <i>Cirsium scariosum</i> var. <i>citrinum</i>)"	35
35	"Plant generally stemless, or stemless and occasionally short-stemmed individuals in population"	36
35	"Plant generally with evident branched or unbranched stem, or occasional stemless individuals present in population"	37
36	"Main leaf spines generally 2--7(10) mm; Teh, WTR, PR"	"Cirsium scariosum var. citrinum"
36	"Main leaf spines generally (3)7--10(12) mm; s CCo (sw San Luis Obispo, nw Santa Barbara cos.)"	"Cirsium scariosum var. loncholepis"
37	"Stem generally erect, proximally unbranched; heads generally +- tightly clustered at stem tip; corolla 20--28 mm"	"Cirsium scariosum var. scariosum"
37	"Stem generally branched proximally or throughout, plant often growing as low, rounded mound; most heads on short to +- long lateral branches; corolla 26--36 mm"	38
38	"Inner phyllary tips generally expanded as scarious, irregularly toothed appendage --- KR, nw MP"	"Cirsium scariosum var. robustum"
38	"Inner phyllary tips acuminate, entire or rarely toothed"	39
39	"Main leaf spines generally 2--7(10) mm; Teh, WTR, PR"	"Cirsium scariosum var. citrinum"
39	"Main leaf spines generally (3)7--10(12) mm; s CCo (sw San Luis Obispo, nw Santa Barbara cos.)"	"Cirsium scariosum var. loncholepis"
40	"Outer phyllaries +- equal, narrowly lanceolate, rigidly spreading, tip-spines 5--10 mm; middle and inner phyllaries +- graduated, bodies appressed, tips spreading, spineless --- s SnFrB (Palo Alto, Santa Clara Co.)"	"Cirsium praeteriens"
40	"Outer and middle phyllaries +- equal or graduated, tips ascending to spreading, needle-like to linear or lanceolate; middle phyllaries spine-tipped"	41
41	"Phyllary tips conspicuously connected side-to-side by network of cobwebby or multicellular hairs"	42
41	"Phyllary tips glabrous or hairy to densely tomentose but generally not conspicuously connected side-to-side by network of cobwebby or multicellular hairs"	45
42	"Corolla lobes thread-like, tips knob-like; style included or exserted 1--2 mm; stem +- hairy, hairs coarse, jointed, generally also cobwebby to densely tomentose with long, fine hairs"	"Cirsium brevistylum"
42	"Corolla lobes linear, tips not knob-like; style conspicuously exserted; stem cobwebby to densely tomentose, hairs long, fine"	43
43	"Plant compact, low-growing, stemless or proximally branched, rounded, mound-like; heads generally not much elevated above leaves --- CCo"	"Cirsium occidentale var. compactum"
43	"Plant erect, main stem generally 1, proximally unbranched; heads generally elevated above leaves"	44
44	"Phyllary tips +- equal, all needle-like, 13--30 mm; corolla light purple to rich red-purple or red"	"Cirsium occidentale var. coulteri"
44	"Phyllary tips +- graduated, outer generally < middle and inner, +- needle-like to lanceolate, 5--15 mm; corolla lavender to bright purple"	"Cirsium occidentale var. occidentale"
45	"Corolla red to +- red-pink or bright rose-purple"	46
45	"Corolla white or cream to lavender, purple, or pale rose"	49
46	"Perennial herb, rosettes from runner roots; corolla throat +- abruptly narrowed to tube; corolla +- bright rose-purple"	"Cirsium andersonii"
46	"Biennial; corolla throat gradually narrowed to tube, without a clear external separation between tube and throat"	47
47	"Plant densely white-tomentose; phyllaries persistently white-tomentose (except tip-spines); outer phyllaries generally very long, spreading or reflexed"	"Cirsium occidentale var. candidissimum"
47	"Plant variably tomentose, occasionally +- glabrous in age; phyllaries glabrous to +- loosely tomentose, occasionally some loosely cobwebby hairs extending between adjacent phyllary tips; outer phyllaries short to long, erect to spreading or reflexed"	48
48	"Corolla 20--24 mm, red or dark red-purple; s SCoRO (s Santa Lucia Range, San Luis Obispo Co.)"	"Cirsium occidentale var. lucianum"
48	"Corolla 23--35 mm, generally bright red-pink to red; widespread in CA-FP, W&I, w DMoj"	"Cirsium occidentale var. venustum"
49	"At least some inner phyllaries +- fringed"	"Cirsium remotifolium var. remotifolium"
49	"Inner phyllaries entire"	50
50	"Base of cauline leaves generally clasping with expanded basal lobes; leaf veins generally prominently raised abaxially"	"Cirsium cymosum var. cymosum"
50	"Base of cauline leaves generally not clasping with expanded basal lobes; leaf veins not prominently raised abaxially"	51
51	"Phyllary tip-spine generally 1--3 mm; SCoR and c SNF to mtns of SW"	"Cirsium occidentale var. californicum"
51	"Phyllary tip-spine generally 3--10 mm"	52
52	"Involucre, including phyllary tips generally ovoid to +- spheric; tip-spines of phyllaries (2)3--6 mm; outer phyllaries generally spreading or ascending --- SNH, GB"	"Cirsium inamoenum var. inamoenum"
52	"Involucre, including phyllary tips often wider than long; tip-spines of phyllaries generally 5--10 mm; outer phyllaries often reflexed"	"Cirsium neomexicanum"