76 EVERGREENS OF COLORADO 



Fig. 23. Engelmann Spruce, Picea engelmanni. 



a. Terminal portion of twig showing fine hairy covering of surface among 



the needle bases, enlarged three times. 



b. Cross-section of a needle, enlarged ten times. 



Fig. 24. Engelmann Spruce, Picea engelmanni. 



a. Twig with mature cones, three-fourths natural size. 



b. Seeds, natural size. 



Fig. 25. Douglas Fir, Pseudotsuga mucronata. Vigorous young tree 40 feet tall and 

 trunk 11 inches in diameter. North Cheyenne Canyon. 



Fig. 26. Douglas Fir, Pseudotsuga mucronata. Showing rough, coarsely ridged bark of 

 old tree. Estes Park. 





 Fig. 27. Douglas Fir, Pseudotsuga mucronata. 



a. Portion of branch bearing staminate flower cones among the needles, 



and two pistillate flower cones at the tips of twigs. Two mature 

 cones of last season are seen hanging from the lower part. About 

 one-half natural size. 



b. Mature cone. 



c. Seeds, two-thirds natural size. 



Fig. 28. Douglas Fir, Pseudotsuga mucronata. 



a. Portion of twigs from which the needles have fallen, leaving small 



oval scars. Enlarged twice. 



b. Cross-section of a leaf enlarged ten times. 



c. Terminal part of twig showing needles attached. Enlarged twice. 



Fig. 29. Douglas Fir (a) and Blue Spruce (b) differ in the behavior of their bud 

 scales in spring. In the first the bud scales remain at the base of the new 

 growth for a time ; in the second they are pushed off on the tips of the new 

 growth. 



Fig. 30. White Fir, Abies concolor. 



a. Tree 30 feet tall with trunk 12 inches in diameter. 



b. Tree trunk of moderate age, 18 inches in diameter. North Cheyenne 



Canyon. 



Fig. 31. White Fir, Abies concolor. 



a. Small portion of twig showing needles and circular needle-scars, en- 



larged one and one-half times. 



b. Cross-section of a needle showing two resin tubes close to the lower 



surface, enlarged eight times. 



Fig. 32. White Fir, Abies concolor. Portion of branch bearing nearly mature cones, 

 one-half natural size. 



Fig. 33. Alpine Fir, Abies lasiocarpa. Unusually perfect form of this tree with trunk 9 

 inches in diameter. Pennock Creek. 



Fig. 34. Alpine Fir, Abies lasiocarpa. Trunk of vigorous tree 12 inches in diameter. 



Fig. 35. Alpine Fir, Abies lasiocarpa. 



a. Terminal shoot of young tree bearing full grown cones ; about one- 



half natural size. 



b. Section of a needle showing two resin tubes midway between upper 



and lower surfaces of the leaf, enlarged about ten times. 



