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 of 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. 
(b) Externally ashy-gray Abies concolor. 
Bark of the trunk scaly, the small scales easily detached Abies balsamea. 
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