THE GENUS EUCALYPTUS. 221 



have been planted in the neighbourhood of Parrainatta, and after 

 having stood for more than half a century, they are still only 

 small trees ; whilst the stringy barks which have sprung up in 

 some of the paddocks that were cleared in the early days of the 

 colony, are only in their youth. In some trees, the age may be 

 ascertained by counting the concentric circles, but this is liable 

 to much fallacy, and it can only be relied on in trees having 

 marked separations between the circles. These circles are clear 

 enough in some of the younger trees of our forests, but as the 

 trees advance in age, many of them have a tendency to become 

 hollow in the centre ; and even in those which are sound at the 

 heart, the circles are frequently obliterated and confused. The 

 late Professor Balfour, in referring to this mode of calculating 

 the ages of trees, remarked that the "calculation can be made with 

 tolerable correctness in trees of temperate and cold climates, where 

 during the winter there is a marked interruption to growth, and 

 thus a line of demarcation is formed between the circles ; but in 

 trees of warm climates, this mode of estimating age may lead to 

 error. It would appear that in these is often the appearance of 

 numerous circles in one year. The age of 5000 years, attributed 

 to some baobabs in Senegal, may be accounted for in this way. 

 Even in trees of Britain, when they get old, it is found that the 

 different circles are so blended as to make it difficult to count 

 them accurately."- The slight change, which ten or twenty years 

 make in some of our bush trees, is incidentally noticed in 

 " Sir Thomas Mitchell's Expeditions" (vol. 2, p. 19), where that 

 writer assures us, that the tree which had been marked by Mr. 

 Oxley nineteen years before, was apparently but little altered in 

 its girth, "judging from the letters which were still as sharp as 

 when first cut, only the bark, having overgrown part of them, 

 had been recently cleared away a little as if to render the 

 letters more legible." In a country, in which the seasons are 

 irregular, and in which sometimes a long continued drought 

 almost puts a stop to vegetation, it seems unlikely that calcu- 

 lations formed on the concentric circles of trees would lead to 

 any solution of the problem regarding their longevity, even if 

 other circumstances were favourable for such an investigation. 

 It is more reasonable to imagine, that the notches cut in some of 

 the gum trees by the aboriginal natives, compared with the known 



