Some Common Hardwoods. 



397 



Since we have ulieady a relation between diameter and age, we 

 -can now establish a relation between height and age from the 

 .graph of height and diameter, and plot the new curve. This 

 method enables one to study the forest where, as yet, no felling is 

 .going on, and it embraces all trees from the youngest to the oldest. 

 Ihe method has no value Avhen once age classes, growing in close 

 canopied forest, are available, but these will not he available until 

 jperhaps a century or more has passed, and in the meantime we 

 want some basis for our working plans. It may be objected that 

 the method would break down owing to the variability in the 

 height of the trees. How^ever, under a given set of conditions the 

 -variations revolve round a mean, and in the case of Mountain Ash 

 the given set of conditions are rather rigid. If we vary one of 

 these conditions, Mountain Ash ceases to grow, and another 

 ^eucalypt takes its place. Messmate (E. obliqua), grows under 

 widely differing sets of conditions, but each set of conditions has 

 its own height growth curve. The method adopted in this paper 

 is applicable to any species growing under the same set of condi- 

 i;ions in any one locality. 



Years of Growth 

 Fig. il. 



The figures for height grqwth were obtained mainly at Powell- 

 town, but measurements were also taken at Belgrave, Warburton 

 and the Ada Creek. Observations have also been made at Upper 

 Yarra, Cumberland Creek, and Beech Forest. In the latter forest, 



