159 



the number of cones which the tree bears : and we conclude that, 

 although the cones may be small, yet there are so many of them 

 that there will be no lack of seeds. 



It is more difficult to trace the age of a hemlock limb than of 

 many other kinds of trees, yet we can easily determine that many 

 of the leaves are several 3^ears old when they fall. 



The bark of the hemlock is used in tanning leather. The tree 

 is much used for lumber. Where does it grow ? 



The arbor-vit^. 



One might almost wonder, at first sight, if the arbor-vitae 

 (often, but wrongly, called white cedar) has any leaves at all. 



49. Spray of the hemlock. Two-thirds natural size. 



It does possess them, however, but they are very different in size 

 and shape from any of the others which we have examined. 

 They are small scale-like bodies, closely pressed together 

 along the sides of the branchlets, in four rows. I^eaves pressed 

 to the branches in this manner are said to be "appressed." 

 The leaves of the arbor-vitae are so close together that they overlap 

 one another. The leaves are of two distinct shapes, sometimes 

 known as the surface leaves and the flank leaves. The former are 

 located on what appears to be the flattened surface of the branch- 

 lets, while the latter are on the sides or edges. See Fig. 50. 

 If we carefully look at the leaves, we shall notice a raised spot 



