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FOC | Family List | FOC Vol. 4 | Cupressaceae

2. Thuja Linnaeus, Sp. Pl. 2: 1002. 1753.

崖柏属 ya bai shu

Trees or shrubs evergreen, monoecious; branchlets arranged in a plane, flattened. Leaves 4-ranked, scalelike, base decurrent only on leading branchlets, dimorphic along branchlets: facial pairs obovate-rhombic; lateral pairs boat-shaped, ridged abaxially, less than 4 mm, overlapping facial pairs, without conspicuous, white stomatal bands abaxially. Pollen cones with (4 or)6-10(-16) microsporophylls, each with (2 or)3 or 4 pollen sacs. Seed cones terminal, solitary, dehiscent when mature in 1st year; cone scales 8 or 10, decussate, flat, only middle, larger 2 or 3 pairs fertile, each fertile scale bearing 1 or 2 seeds; free bract apex a very short mucro. Seeds flat, with 2 lateral, narrow wings. Cotyledons 2.

Five species: E Asia, E and W North America; five species (one endemic, three introduced) in China.

1 Leaves obtuse at apex, rarely subacute.   (2)
+ Leaves subacute to acuminate at apex.   (3)
2 (1) Facial leaves without a gland; young branchlets not glaucous   1 Thuja sutchuenensis
+ Facial leaves with a gland; young branchlets ± glaucous   2 Thuja koraiensis
3 (1) Leaves acuminate at apex; lateral leaves longer than facial leaves, apex straight   3 Thuja plicata
+ Leaves acute or subabcute at apex, lateral leaves slightly shorter than or as long as facial leaves, apex incurved.   (4)
4 (3) Facial leaves with a conspicuous abaxial gland   4 Thuja occidentalis
+ Facial leaves without a gland   5 Thuja standishii

Lower Taxa


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