Leaves opposite, simple or compound and then pinnately or ternately divided 1–3 times.
Flowers in paniculate inflorescences [or solitary and axillary or terminal], actinomorphic, unisexual [or bisexual]. Sepals 4 or rarely more, petaloid, valvate, white or reddish [or blue or yellow]. Petals absent [or minute]. Stamens many, petaloid staminodes sometimes present. Carpels many.
Fruit a globose head of achenes, each with a persistent, elongated, often plumose style.
| ||Key to the species|| |
|1||Leaves simple to ternate or imparipinnate, with 5(-7) or fewer leaflets, anthers with or without an apically protruding connective appendage||2|
|Leaves biternate, triternate or flammuliform with more than 5 leaflets; anthers without an apically protuding connective appendage||5|
|2||Plants deciduous with bisexual flowers||Clematis montana |
|Plants evergreen, dioecious; (female flowers with one whorl of staminodes)|
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|3||Leaf margins usually entire; connective appendage to 0.5 mm long; tepals 0.7–2.5 cm long||4|
|Leaf margins serrate;connective appendages 1–3 mm long; tepals 1.3–3.5 cm long|
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|4||Achenes often with distinct longitudinal ridges on each lateral face, often more or less falcate, tepals 0.7–1.6 cm long; anthers mostly 1–1.5 mm long; connective appendage 0.2–0.5 mm long||Clematis pinkeringii|
|Achenes neither ridged nor falcate; tepals 1.1–2.5 cm long; anthers mostly 1.5–2 mm long, connective appendage 0.2–0.5 mm long|
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|5||Achenes fusiform. c. 1 mm diameter; leaflets usually serrate-dentate||Clematis fawcettii|
|Achenes distictly compressed, broader than 1 mm, leaflets usually entire ot sometimes deeply lobed|
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|6||Leaflets usually biternate with up to 9(-12) leaflets, sometimes with leaflets lobed||Clematis microphylla|
|Leaves flammuliform to triternate with more than 12 leaflets (rarely fewer in some immature leaves)|
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|7||Leaflets usually 12–15 per leaf, broadest below the middle; terminal leaflet 12–45 mm long||Clematis decipiens|
|Leaflets usually 18–36 per leaf, broadest beyond the middle towards the leaf tips; terminal leaflet 5–15 (-25) mm long|
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