86 HISTORICAL NOTICE OF CELEBRATED TREES. [June 



an unsafe criterion, so that this method can seldom be employed 

 with much confidence. A more common mode, therefore, is to 

 employ the average rate of growth of the oldest trees of which 

 complete sections have been examined, for the approximate deter- 

 mination of the age of remarkably large trunks of the same species, 

 when the size alone is known ; for repeated observations prove that 

 the increase is greatest (that is, that the layers are thickest) in 

 young trees ; but that afterwards — say, after the first century — the 

 tree increases in diameter at a much slower, but somewhat uniform 

 rate, which does not greatly vary in different trees of the same 

 species. Such estimates, therefore, would always tend to underrate, 

 rather than to exaggerate, the age of a large tree. But it is really 

 unsafe to apply this method except 'to truly venerable trunks, for 

 the growth of a tree is liable to great variations during the first 

 century or two ; either from year to year, or between different 

 individuals of the same species. The influence of a stratum of soil, or 

 the injury of a single leading root or branch, may affect the whole 

 growth of a young tree for a series of years, while in an older 

 individual the wide distribution of the roots, and multiplication of 

 the branches, render the effect of local injuries nearly unappreciable, 

 and the influence of any one or more unfavourable seasons is lost, 

 in the average of a great number. But more commonly, perhaps, 

 our estimates rest, either wholly or in part, upon historical evidence 

 or tradition ; and in Europe many trees, especially chestnuts, lime- 

 trees, oaks, and yews, may be satisfactorily traced by records 

 throughout several centuries. 



Having thus indicated the kinds or sources of evidence which are 

 brought to bear with more or less directness and force upon the 

 age of trees, I now offer an account of some of the more remarkable 

 or curious cases that have been noticed. 



THE BAOBAB. 



The Baobab or monkey-bread, Adansonia digitata, has long 

 afforded the most celebrated instances of vegetable longevity : 

 Humboldt indeed calls them " the oldest organic monuments of our 

 planet." They are not uncommon on the western coast of Africa. 

 The tree is remarkable for the small height it attains, compared with 

 the immense diameter of the trunk and length of its branches. 

 Trunks which are 70 or 80 feet in circumference rise to the height 

 of only 10 or 12 feet, when they divide into a great number of 

 extremely large branches, 50 or 60 feet long, which, spreading 

 widely in every direction, form a round verdant mass perhaps 150 

 feet in diameter, and only 70 feet in height. The roots likewise are 

 of vast length: one of these, laid bare by a torrent which had 



