8 



I. Abies lasiocarpa (Hook.) Nutt., Sylva 3: 138. 1849. 



20-30 m. high, with pale, thin, smooth, light-gray bark; 

 leaves dark green, pointed; cones oblong-cylindrical, 6-7 cm. 

 long, 3-4 cm. in diameter, purplish-brown; scales nearly orbicular 

 or quadrangular, 12-20 mm. long and broad; seeds about 6 mm. 

 long, with dark lustrous wings. Alpine Fir; Balsam. 



Colorado and Wyoming to the Northwest. 



In this species, the resin ducts are in the chlorophyl-bearing 

 tissue, midway between the upper and lower epidermis. 



2. Abies concolor (Gord.) Parry, Am. Nat. 9: 204. 1875. 



25-50 m. high, with a diameter of 6-12 dm., and rough grayish 

 bark; leaves mostly obtuse, pale green; cones oblong-cylindrical, 

 7-12 cm. long, 3-4 cm. in diameter, pale green or sometimes 

 purplish; scales 25-30 mm. wide, about half as high; seeds 8-12 

 mm. long, brown, with rose-colored wings. White Fir. 



Colorado to California and thence northward. 



In this species, the two resin ducts are next to the lower 

 epidermis. 



Both these species have the xylem divided, distinguishing 

 them (in addition to the position of the stomata) from the 

 following genus, which has the xylem undivided. 



IV. PSEUDOTSUGA. 

 One species. i. P. taxifolia. 



I. PsEUDOTSUGA TAXIFOLIA (Lam.) Brittou, Trans. N. Y. Acad. 

 Sci. 8: 74. 1889. 



35-75 m. high, 1-4 m. in diameter, with thick, deeply fissured, 

 brown bark; leaves flat, 15-25 mm. long; cones 5-10 cm. long, 

 subcylindrical ; bracts exserted, 3-pointed, giving the cones a 

 fringed appearance; seeds 6 mm. long, on upper side reddish- 

 brown, on lower flat and white, winged. Douglas Spruce. 



Throughout the Rocky Mountains to the coast. 



This genus may be easily distinguished from the species of Abies 

 in our range in two ways : the stomata are found only on the lower 

 surface, and the xylem of the bundle is undivided, while in 

 Abies stomata are present on both surfaces, and the xylem is 

 divided. 



University of Wyoming, 

 Laramie, Wyo. 



