Thuy 



a 191 



THUYA OCCIDENTALIS, Western Arbor Vit^ 



Thuya ocddentalis, Linnseus, Sp. PI. 1002 (1753); Loudon, Arb. et Frut. Brit. iv. 2454 (1838); 



Sargent, Silva N. America, x. 126, t. 532 (1896), and Manual Trees N. America, ia, (1905); 



Masters, Gard. Chron. xxi. 213, figs. 67, 68, and 258, fig. 86 (1897); Kent, in Veitch's Man. 



Conif. 244 (1900). 

 TTiuya plicata, Hort. {non Don). 



A tree, attaining a height of 50 to 60 feet, with a stout and buttressed trunk, some- 

 times 6 feet in diameter. It often divides near the base into two or three stems. 

 In England the branches, short and spreading, form a tree pyramidal in outline, 

 which is not so dense in foliage as Thuya plicata. Bark of the trunk scaling off in 

 thin papery rolls, but not so freely or so finely as in Thuya japonica. The branches 

 when of no great size begin to show scaly bark. 



The branch systems are disposed in horizontal planes, resembling those of 

 Thuya plicata ; but their main axes are flattened, being compressed from below 

 upwards, while the leaves are shorter than in that species, ending in similar long 

 points. The flat leaves on the main axes are studded with conspicuous large 

 circular elevated glands. The smaller leaves on the ultimate branchlets vary as 

 regards the presence or absence of glands ; the lateral pairs are shorter than and not 

 so acutely pointed as in Thuya plicata. The foliage is dark green above, pale green 

 and not marked with white streaks below. 



The male flowers, minute and globose, are composed of three decussate pairs of 

 stamens. The female flowers are yellow. 



The cones become deflected when ripe, as in Thuya plicata. They are oblong, 

 light brown, and composed of 4 to 5 pairs of scales, of which the 2nd and 3rd pairs are 

 larger than the others, and fertile. The scales are ovate or spathulate, ending in a 

 rounded or acute apex, with a minute external process, which is generally much less 

 developed than is the case in Thuya plicata. The seeds, usually two on each fertile 

 scale, are scarcely distinguishable from those of the last-named species. 



Seedling} Cotyledons as in Thuya plicata. The caulicle and stem are quad- 

 rangular. The first two true leaves are opposite, spreading, and similar to the 

 cotyledons, though smaller. These are followed by 5 or more whorls or pseudo- 

 whorls, each of three similar leaves, linear, acute, and sessile. The ultimate leaves 

 are opposite, decussate, and adnate for the greater part of their length to branchlets, 

 which are flattened from above downwards. 



Varieties 



Few trees, except Cupressus Lawsoniana, show a greater tendency to varia- 

 tion in the seed-bed. Sargent says that if anyone will sow a quantity of seed 

 he will be sure to find forms among the seedlings as novel and as interesting 



' See Lubbock, Seedlings, ii. 548, 560 (1892). 



