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A deciduous climber with slender angled stems, downy when young, more especially near the swollen joints. Leaves mostly bi-ternate, i.e., consisting of three main divisions, each having three leaflets – or nine in all; the whole leaf
3 to 6 in. long. Leaflets ovate to lance-shaped, pointed, rounded or tapered at the base, coarsely and irregularly toothed; 1⁄2 to 11⁄2 in. long, 1⁄4 to 3⁄4 in. wide; nearly or quite glabrous except at the junction of the slender leaf-stalks. Flowers 21⁄2 to 4 in. wide, produced from May or June onwards at the end of the shoots or at the joints, each on a slender stalk 3 in. or more long. Sepals four, blue or violet-blue; 11⁄4 to 2 in. long, 1⁄4 to 1⁄3 in. wide; pointed. The centre of each flower is filled with a large number of petal-like segments decreasing in size towards the middle, the outer ones narrow, elliptic, pointed, and violet-blue like the sepals, the innermost of linear shape and almost white; all clothed with down. Stamens numerous, anthers pale yellow. Seed-vessels terminated by a slender, feathered style, 11⁄2 in. long. Bot. Mag., t. 9142.
Native of the province of Kansu, China, and of Siberia; first introduced by Purdom (No. 149), to the Coombe Wood nursery where it flowered in July, 1912; afterwards by Reginald Farrer (No. 315) about 1914. This beautiful climber belongs to the Atragene section of Clematis. Previous to its introduction this group was represented in gardens by only two species – C. alpina and C. verticillaris. These species are distinguished by the crowd of petal-like organs (staminodes) coming between the stamens and sepals. C. macropetala was collected about 1742 by d’Incarville in the mountainous country north of Peking, and it was named and first described by Ledebour in 1829 from a plant found in Siberia. It is closely akin to C. alpina, but the sepals are narrower, the petal-like organs longer, narrower and pointed (those of C. alpina being shorter, spathulate and blunt). C. macropetala is also later-flowering.