UNITED STATES DEPARTMENT OF AGRICULTURE 



i BULLETIN No. 680 



Contribution from the Forest Service 

 HENRY S. GRAVES, Forester 



Washington, D. C. 



PROFESSIONAL PAPER 



August 14, 1918 



MISCELLANEOUS CONIFERS OF THE ROCKY 

 MOUNTAIN REGION. 



By George B. Sudworth, Dendrologist. 



CONTENTS. 



Scope of bulletin 1 



Generic characteristics of larches 2 



Tamarack, Larix laricina (DuRoi) Koch. . . 3 



Western larch, Larix occidentalis Nuttall. . . 5 



Alpine larch, Larix lyallii Parlatore 8 



Generic characteristics of hemlocks 11 



Western hemlock, Tsuga heterophylla (Raf .) 



Sargent 12 



Mountain hemlock, Tsuga mertensiana 



(Bong.) Sargent 16 



Generic characteristics of ffilse hemlocks 19 



Douglas fir, Pseudotsuga taxifolia (Poir) 



Britton 21 



Generic characteristics of incense cedars 27 



Incense cedar, Libocedrus decurrens Torrey. 28 

 Generic characteristics of arborvitaes — "Ce- 

 dars" 32 



Western red cedar. Thuja plicata D. Don. . 33 



Family relationships of yew trees 39 



Generic characteristics of yew trees 40 



Western yew, Taxus brevifolia Nuttall 41 



Key to Genera and Species 44 



List of Publications 45 



SCOPE OF THE BULLETIN. 



This bulletin deals with the distinguishing characteristics, forest 

 habits, and geographic distribution of all the larch, hemlock, false- 

 hemlock, incense cedar, arborvitse, and yew trees that grow naturally 

 within the Rocky Mountain region. The extent of the territory 

 included in this region is indicated in a recent publication on ' ' The 

 Cypress and Juniper Trees of the Rocky Mountain Region," ^ which 

 also contains a full discussion of the class and family relationships of 

 the true coniferous trees here described, as well as information applica- 

 ble in the present case regarding the method of treating the subject, 

 the sources from which data on the geographic range of trees were 

 obtained, and the like. Acknowledgments made in the above- 

 mentioned publication of assistance received apply also in the case 

 of the present bulletin. 



Keys for the identification of genera and species are provided on 

 page 44. 



49432° 



1 Bulletin No. 2"t7, U. S. Departmont of .\n:rieu!ture, p. 1, 1915. 



-18— Bull, eso— 1 



