THE SPECIES. 37 



Park. It is called " blue spruce," because of the blue-green cast of 

 its foliage, and is of some interest as being the " State tree " of Colo- 

 rado. It is also known as Picea Parryana. 



The blue spruce is a small tree and differs from Engelmann spruce 

 in having smooth instead of pubescent twigs. In its growth it usually 

 preserves a conical form, but often spreads its branches wide, and 

 may be reduced to a shrubby form at high altitudes. The bark is 

 gray, usually smooth and firm, in older trees becoming hard and 

 thick. The twigs are shiny and smooth and the leaves about 1 inch 

 in length and sharp pointed. Cones are usually plentiful, borne 

 singly or in clusters, and 3 or 4 inches long. 



The wood of this tree is of little importance commercially, but the 

 trees are exploited much by horticulturists for ornamental planting 

 and are widely grown throughout the country. 



HEMLOCKS. 



Four species of hemlock are native to North America. Two of 

 these occur on the Atlantic coast and tw/o on the Pacific. The hem- 

 locks, like the spruces, prefer a cool climate and moist soil ; they are 

 also partial to regions of relatively high atmospheric moisture. 

 They are trees that endure much shade and often grow in great 

 numbers under other trees in a forest ; veritable thickets of young 

 trees sometimes occur in such situations. In form the hemlocks have 

 some features that are distinctive. The leading shoot of the tree 

 has a more or less horizontal or nodding habit for a foot or two of 

 its length; the branches, at least the secondary ones, usually droop, 

 and there are many small twigs which, though originating on sev- 

 eral sides of the 

 branch, come to be 

 distributed in a 

 more or less flat 

 spray. 



In its botanical 

 aspects the tree 

 may be described 

 as follows: Its 

 leaves are usually 

 much flattened and 

 at the base nar- 

 rowed into a stalk 



that becomes FlG> 20- West ern Hemlock. A, Twig and cone ; B, seed-bearing 



scale ; slightly enlarged. 



twisted in order to 



bring the upper surface of the leaf into the plane occupied by the 

 spray of branches. The leaves are, short and usually lighter colored 

 beneath ; they fall from the branch rapidly upon drying and leave a 



