232 TRANSACTIONS OF ROYAL SCOTTISH ArvBOllICULTUKAL SOCIETY. 



213 feet, with a diameter of 6i feet, measured at 6^ feet above 

 the ground. Iti the same locality, on gravelly soil, the trees only 

 reached an average height of 148 feet, and a diameter of 26 feet. 

 Again, in the Rocky Mountains, in Montana, at the same elevation 

 and degree of latitude as on the west coast, the Douglas fir reaches, 

 on best soils only, the same dimensions as on the gravelly soil of the 

 Cascade Range Mountains, that is to say, a height of 148 feet, and 

 a diameter of about 2'6 feet. The latter dimensions are not more 

 than what our silver fir will attain in localities of the first quality. 

 The part of the Cascade Range where the Douglas fir grows, has 

 an annual rainfall of about G4 inches, while in Montana only 24 

 inches fall. Dr Mayr believes that the development of the Douglas 

 fir is proportionate to the rainfall ; respectively to the degree of 

 moisture in the air. 



(Ad. 4.) The cross-section in question was sent from America 

 for exhibition in Europe ; it was then made over to Kew, and by 

 the kindness of the Director of Kew Gardens it was lately presented 

 to the Cooper's HUl Forest Museum. The section shows a total 

 diameter, including the bark, of 7 feet 9 inches, and the counting 

 of the concentric rings indicates a total age of 515 years. A careful 

 examination of the section has yielded the results exhibited in the 

 subjoined table : — 



