79 



This genus comprises about 18 to 20 known species, of which num- 

 ber 8 are found in North America, 3 in the eastern part and 5 in the 

 western part. Two of the eastern species are native to Pennsylva- 

 nia. In addition to the native species 2 species, exotic to the State, 

 are commonly planted for ornamental purposes, viz., the Norway 

 Spruce (Picea Abies (L.) Karst), and Colorado Blue Spruce (Picea 

 pungens Engelm.). The subjoined key will distinguish the Spruces 

 commonly found in Pennsylvania. 



KEY TO THE SPECIES. 



Page. 

 1. Cones cylindrical, over 3 inches long; terminal part of lateral branchlets pendulous; 



leaves slender, dark green, glossy, sharp-pointed, P. Abies 82 



1. Cones ovate to oblong, less than 3 inches long; terminal part of lateral branchlets 



not decidedly pendulous; leaves rather stout, often blunt-pointed, 2 



2. Leaves dark yellowish-green; cones elongated-ovoid with clear brown, entire-margined 



scales P. rubra- 80 



2. Leaves bluish-green; cones short-ovoid; often persisting beyond first season; cone-scales 



dull, grayish-brown with jagged margin P. mariana 81 



