690 JOURNAL OF FORESTRY 



Comparing the height growth in U. S. A. quality I with that of qual- 

 ity II in Britain, the trend of the two curves is found to be very dif- 

 ferent. The American trees grow comparatively slowly at first, attain- 

 ing a height of 36 feet at 20 years compared with 44 feet in Britain. 

 Between 20 and 30 years the growth is virtually the same, as increase 

 of 25 feet of height being given by both curves ; in the next decade, 

 however, there is a marked difference in favor of the American trees, 

 which put on 23 feet of height against the 17^^ feet shown in British 

 tables, and in the following ten years 18 feet against 14 feet in the 

 British tables. 



When the volumes of the equivalent quality classes are compared, 

 the American woods are seen to have a lower volume for a given age 

 and height than in Britain for the first 40 years. At 50 years U. S. A. 

 quality I and British quality II both show a volume of 7.100 cubic feet 

 per acre. 



The marked effect of increasing exposure and elevation upon the 

 rate of growth of larch stands out clearly from the investigation. It 

 appears to be the most sensitive of the species in that respect. None 

 the less, on moderately or well-sheltered slopes up to about 1,000 teet 

 elevation in Wales, the west of England and Scotland, it is capable of 

 producing large crops of valuable timber. 



The importance of soil conditions for the growth of Scots pine 

 comes out clearly from this review. In this respect Scots pine is in 

 strong contrast to larch and spruce, in which soil conditions appear to 

 play a relatively small part. The reason probably is that the latter 

 species have been planted mainly on soils derived from the weathering 

 of ro.-k in situ yielding usually deep, fertile sandy loams or loams, 

 and there is a wide margin of safety. Scots pine, on the other hand, 

 has been largely planted on transported soils or on formations such as 

 the Bagshot sands, which are initially poor in food materials, and the 

 margin of safety is small. Moreover, the occurrence of the majoritv 

 of the Scots pine on fiat ground tends in the same direction, i. e., lo 

 reduce the margin of safety, for pan formation is much more liable 

 to take place on fiat than on sloping ground, the effect of which is 

 often to hold up water and prevent the necessary aeration of the roots, 

 besides checking root development in a downward direction. 



Apart from the more recently introduced exotics such as Douglas 

 fir and Sitka spruce, the Norway spruce is seen to be the best volume 

 producer of English conifers. It is especially useful as a timber-pro- 

 ducing tree at the higher altitudes, where its good height-growth and 



