THUYA 



Thuya} Linnaeus, Gen. PL 378 (1737); R. Brown, Trans. Edin. Bot. Soc. ix. 358 (1868); Bentham 

 et Hooker, Gen. PL iii. 426 {ex parte) (1880); Masters, ywr. Linn. Soc. {Bot.) xxx. 19 (1893). 

 Biota, Endlicher, Syn. Conif.,^"] (1847). 



Evergreen trees of pyramidal habit and aromatic odour, belonging to the tribe 

 Cupressineae of the order Coniferae. Branches spreading and much ramified, 

 terminating in so-called " branch-systems," which are flattened in one plane and are 

 2-, 3-, or 4- pinnately divided, their primary and other axes being densely clothed with 

 scale-like leaves. These branch-systems ^ when they fall are cast off as a whole, the 

 leaves not falling separately. The leaves, which are minute, are more or less 

 coalesced with the axes, on which they stand in 4 ranks in 2 decussate pairs, those 

 of the lateral ranks being conduplicate or boat-shaped, those placed dorsally and 

 ventrally being flattened. In the seedling stage and certain horticultural varieties,* 

 the foliage is different, the leaves being acicular, spreading, and uniform ; all 4 ranks 

 in this case are alike. 



Flowers monoecious, all solitary and terminal on the ultimate short branchlets of 

 the preceding year, the male and female flowers on different branchlets, the former 

 on the branchlets near the base of the shoot, the latter on those near its summit. 

 Male flowers cylindrical or globular, consisting of 3 to 6 pairs of stamens placed 

 decussately on an axis, each with an orbicular connective bearing 2 to 4 pollen sacs. 

 Female flowers minute cones, composed of opposite scales in which no distinction of 

 ovular scale and bract is visible, continuous in series with the leaves at the end of 

 the branchlet, 2 to 4 pairs in Biota, 4 to 6 pairs in Euthuya, mucronate at the apex, 

 some sterile, the others fertile and bearing 2 to 3 ovules. 



Cones solitary, ultimately deflected, except in Biota, in which they retain the 

 erect position, oblong, ovoid, or almost globose, composed of 3 to 6 pairs of decussate 

 scales, which are not peltate, some fertile, the others sterile, the uppermost often 

 united together. Seeds 2 to 3 on each fertile scale. Cotyledons 2. 



The genus Thuya, as understood here, does not include Chamsecyparis and 



' Thuya has been written Thtija in Linnaeus, Hort. Cliff. 449 (1737), and Sp. PI. 1002 (1753) ; ami T/iuia in Scopoli, 

 Introd. 353 (1777). 



" The branchlets become brown in colour before they fall. See Masters, Gard. Chron. 1883, xx. 596. 



' In addition to the varieties, in which the foliage retains permanently the seedling character, other forms occur in 

 cultivation, in which the leaves are intermediate in shape between those of the seedling and of the adult plant. These varieties 

 resemble the so-called Retinospora forms of the genus Cupressus, and were formerly considered, like them, to belong to a 

 distinct genus. 



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