1. PiCEA Engelmannii (Parry) Engelm., Trans. Acad. Sci. 



St. Louis, 2: 212. 1863. 



25-40 m. high, much dwarfed and shrub-Hke at high elevations; 

 branchlets puberulent; bark light-reddish; leaves 2-3 cm. long, 

 abruptly acute; cones oval or oblong, brown, about 5 cm. long. 

 Engelmann Spruce. 



Throughout the Rocky Mountain region from middle to high 

 elevations. 



In the fibro-vascular bundle of the leaves of this species, 

 large, heavy -walled, sclerenchymatic cells are found, usually 

 6-10 in a cluster on the opposite side of the bundle from the 

 woody tissue. This and the following species are difficult to 

 distinguish from each other, except in the field, and in the case of 

 specimens with fully developed cones. The above key has 

 proved satisfactory, if some degree of care be taken in cutting 

 and staining the sections. 



2. PiCEA PUNGENS Engelm., London Gard. Chron. 1879: 334. 



1879. 



Lower than the preceding, conical in growth; bark thick, 

 smooth and gray; branchlets smooth and shining; leaves 2-3 

 cm. long, extremely sharp pointed; cones cylindrical, 6-10 cm. 

 long, light brown. Blue Spruce. 



Colorado, Wyoming, and Utah. 



No additional strengthening cells are found in the bundles of 

 the leaves of this species. The xylem of the bundle appears to 

 be divided very slightly, almost imperceptibly, except under, the 

 higher powers of the microscope. 



In both these species, it is often difficult to get sections showing 

 resin ducts. Sections may be obtained showing two ducts in 

 opposite corners, but most sections will lack this number. It is 

 hoped that this means of distinguishing between the two species 

 will be of value in herbaria, where our two species are so often 

 confused. 



III. Abies. 



Resin ducts in middle of parenchyma. i. A. lasiocarpa. 



Resin ducts next to lower epidermis. 2. A. concolor. 



