80 Proceedings of the Roi/al Irish Academi/. 



A cross-section of the leaf of the Oregon species, viewed with an oi-dinaiy 

 hand lens, appears thin, with a Hat under surface; while ihat of the Colorado 

 species is thick, with a convex under surface. The glaucous or bluish colour 

 of the Colorado Douglas Fir is generally apparent ; Imt this is a variable 

 character, wliich cannot be always relied on. The dilfereiice in the odour of 

 tlie two trees is remarkable, that of P. glavca being strong and like turpentine, 

 while that of P. Boni/Zasii is very agreeable, with a fragrance like pine- 

 apples. This is readily recognized when the leaves are rubbed between the 

 fingers, or when a leafy brancli is placed in water in a room. 



4. Flouna. The female flowers or very young cones are reniarkalily 

 difl'erent in colour and sliape in the two species. (See Plate XIII.) The 

 young cones in the early stage are formed of compaiatively largo bracts, 

 lit the base of each of which is a minute scale, bearing two ovules. In tlie 

 Colorado species the reflexed and spreading bracts form an irregularly shaped 

 body, which is brilliant red in colour. In the Oregon Douglas Fir tlie bracts 

 are all slraiglit, appressed and erect, forming a regular cone, which is usually 

 greenish, rarely i>ink in colour. The male (lowers apparently do not differ in 

 the two species. 



5. Cones. The ripe cones of the Oregon Douglas Fir are large in size, 

 composed of numerous .scales, and with straight nppressed erect bracts. The 

 smaller cones <if the Colorado species have fewer scales, with most, if not all, 

 of the bmcts reflexed about the middle, eitl>er entirely backwards over the 

 scale beneath, or spreading at right angles to the axis of ihe cone. 



6. WtHxK The Oregon Douglas Fir, when grown on a long rotation, as in 

 America, yields excellent timber, large in size, free from knots, straight in 

 grain, liglil in weight, and very durable. It is the strongest wood in the 

 world for its weight that is obtainable in commercial quantities. Quickly 

 grown timber, in this country, unless the rings are extremely wide, is 

 probably equally strong, but is less valuable, having more defects. It ranks 

 in quality between Larcii and Scotch I'ine, but surpasses both in dimensions. 

 It is equally durable with Ijirch, converts well, keeping straight when long 

 sizes are sawn ; and if carefully stacked dries quickly, and is not liable to 

 warp. It has been used for gates, doors, and fencing, and for railway 

 sleepers and pit timber. 



The Colorado Douglas Fir, owing to its small size and mode of growth in 

 open stands, yields as a rule rough timber. It is very strong and durable, 

 but irregular in stnicture. 



A difference in the microscopical structure of the wood of the two species 

 has been lately described.' In the Oregon Douglas Fir the thickened 

 ' G. J. Griffin, iu Journal of ForenU >i, xvi, 813 (1919). 



