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V. 



THE DOUGLAS FIES : A BOTANICAL AND SILVICULTURAL 

 DESCRIPTION OF THE VARIOUS SPECIES OF PSEUDOTSUGA. 



By AUGUSTINE HENRY, M.A., F.L.S., 



AND 



MARGARET G. FLOOD, B.A. 

 (Plates XII— XIV.) 



Kend January 26. PuUished JUv 17, 1920. 



I. — Introduction. 



The Douglas Fir of North America is one of tlie great timber trees of the 

 world. Widely spread over the vast region between the Rocky Mountains 

 and the Pacific Coast, where tlie diversity in climate is extreme, it exists in 

 several forms, remarkably different in growth and utility. It was the 

 primary object, at the outset of this study, to investigate the two chief forms, 

 which are still grouped together by most botanists as a single species, 

 Pseudotsuga Douc/lasii, Carriere. These are, however, more correctly regarded 

 as two species : one, the Pacific Coast, Oregon, or Green Douglas Fir, to 

 which Carriere's name should be restricted, and the other, the Rocky 

 Mountains, Colorado, or Blue Douglas Fir, which Mayr named Pseitdotsin/a 

 (jlauca. These two species inhabit separate regions, and diller much 

 in silvicultural features. The Oregon Douglas Fir forms forests of 

 immense trees on the Pacific Coast, and is now much cultivated 

 in the British Isles, where its rapid growth and enormous yields of 

 timber in a short term of years render it very valuable. The Colorado 

 species, throughout its home in the Rocky Mountains, is much inferior in 

 size and vigour, and is of little or no value in commercial aflorestation in this 

 country. The importance of a comparative study of these two species is 

 unquestionable. 



The original scope of this paper has been extended to include an account 

 of the whole genus. This is given below in a methodical description of the 

 genus and of the seven species wliieh have been distinguished. Our 

 knowledge of P. Doucjlasii and P. ylauca, both in the wild and cultivated 

 states, is fairly complete. Of the other species, the native material for study 



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