196 TRANSACTIONS OF ROVAL SCOTTISH ARBORICULTURAL SOCIETY. 



to its origin, although it is not found exclusively in that State, 

 but along the Rocky Mountains almost from north to south," 

 while P. macrocarpa is described ^ " as a local form inhabiting 

 the San Bernardino mountains in South California, and their 

 continuation into northern Mexico." 



In his Silva of North America Professor Sargent places the 

 Douglas fir under Pseudohuga mucronata (Sudworth), and in his 

 conspectus of the North American species he gives the following 

 as their distinguishing characters : — 



Leaves usually rounded and obtuse at the apex, dark yellow- 

 green or rarely blue-green ; cones small, their bracts 

 much exserted. i. P. mucronata. 



Leaves acuminate at the apex, bluish grey ; cones large, their 

 bracts slightly exserted. 2. P. macrocarpa. 



What seems to favour Professor Schwappach's view that the 

 glaucous-leaved plants grown in British nurseries belong to 

 P. macrocarpa is that, in not a few instances,- the plants have 

 markedly sharp-pointed, blue-grey leaves, and winter-buds which 

 seem to agree more closely in their characters with those of 

 P. macrocarpa, as described by Sargent, than with those of the 

 Douglas fir ; and in yet another particular is there a similarity 

 between the two plants, for, according to Sargent, P. macrocarpa 

 is not only a comparatively small tree, but it is also of slow 

 growth. But as the glaucous-leaved plants which occur in 

 plantations in this country are as yet comparatively young, and 

 as Sargent's descriptions no doubt apply only to plants of more 

 mature growth, too much importance ought not to be attached 

 to such variable characters as the form of the leaf and the shape 

 of the winter-bud, and until the plants reach the cone-bearing 

 stage the question of identity must remain in doubt. Of more 

 importance, perhaps, from a sylvicultural point of view, is the 

 rate of growth of these so-called Colorado plants, as compared 

 with the ordinary type of the Douglas fir, and with other kinds 

 of forest trees ; and it may be of interest to give here some 

 particulars relating to the rate of growth of some of these 

 glaucous-leaved plants which have come under my observation 

 recently. 



* Loc. cit. 



"^ The possibility of two or more distinct forms occurring in nurseries under 

 the name " Colorado variety " has to be kept in view. 



