PINACE.E 523 



TSUGA, Carriere. 

 Hemlock Spruces. 



This genus includes nine species of evergreen trees of pyra- 

 midal habit found in temperate N. America, Japan, Formosa, 

 China, and the Himalaya. Branches horizontal, the branchlets 

 numerous, slender, often pendulous at the tips. Winter buds 

 both terminal and lateral arising from the leaf axils of the 

 current year's shoots. Leaves short, linear, usually blunt, 

 tlirown into a two -ranked arrangement by the twisting of the 

 leaf-stalks, or spreading round the shoots, persistent for several 

 years, closely set on shining, cushion-like projections which are 

 separated by grooves ; resin canals one in each leaf situated 

 between the vascular bundle and the lower surface. Male and 

 female flowers on different branches of the same tree. Male 

 catkins in the axils of the previous year's shoots, consisting of 

 rounded clusters of spirally arranged, two-celled anthers. Female 

 flowers terminating the lateral shoots of the previous year, with 

 roundish scales which are slightly longer than the bracts. Cones 

 solitary, small, pendulous, ripening during the first year, but 

 remaining on the tree until the following summer or autumn of 

 the second year after the release of the seeds ; scales leathery, 

 overlapping ; bracts inconspicuous, usually concealed beneath 

 the scales. Seeds two on each scale with resin vesicles, winged. 



The slender drooping shoots taken in conjunction with the 

 usually two-ranked arrangement of the leaves which have only 

 one resin canal and the slender leaf stalks pressed against the 

 shoot are good distinguishing marks of Tsuga. 



The genus may be naturally divided into two sections as 

 follows : — 



i. Hesperopeuce. 



Branchlets not all in one plane. Leaves spreading all round 

 the shoot, rounded or keeled above, bearing stomata on both 

 surfaces. Cones oblong cylindric, composed of numerous scales. 



ii. Micropeuce. 



Branchlets all in one plane. Leaves pectinate, flat, grooved 

 above, bearing stomata on the lower surface only. Cones ovoid, 

 small, composed of few scales. 



Wood usually without resin ducts, brownish, heartwood rather 

 darker than sap wood, variable in quality and sometimes brittle, 

 at other times of good quality and easy to work. Good qualities 

 are suitable for building purposes and for joinery, whilst much 

 is used for box-making. The bark is rich in tannin and that of 

 some species is used extensively in tanning operations. 



The Hemlock spruces thrive in places where the atmospheric 



