SPRUCE AND BALSAM FIR TREES. 43 



KEY TO ABIES. 



Leaves of lowest branches arranged in two ranks (on two sides of the 



twigs) and mostly notched at the end Abies grandis. 



Leaves of lower branches more or less densely crowded on the upper 

 sides of the twigs and with no notch at the end : 



Bark of the trunk soft and corky Abies arizonica. 



Bark or the trunk hard and tough : 



(1) Irregularly and shallowly seamed Abies lasiocarpa. 



(2) More or less regularly and deeply furrowed and ridged: 



(a) Externally dark reddish-brown A. magnified shastensis. 



(6) Externally ashy-gray Abies coneolor. 



Bark of the trunk scaly, the small scales easily detached Abies balsamea. 



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