82 



IMMENSE GROWTH OF TREES. 



much of the stem be found. In a large proportion of cases these modes will evoke 

 tolerably accurate results ; but there are several sources of fallacy to which we must 

 refer. 



First, it is highly probable that in tropical climates the wood of more than one year 

 may produce but one zone ; for as there is but a short if any period of cessation of 

 growth, but very slight evidences of any line of demarcation can be detected. The 

 real age of trees may thus be underrated. 



Secondly. It is highly probable that in some plants more than one zone of wood is 

 formed in the year; for such is evidently the case in the root of the Beta Vulgaris. 

 This would unduly increase the age of the tree. 



Thirdly. When examining a fragment of a tree the observer should remember that 

 the zones are not of equal thickness throughout, and that it is quite possible that in 

 some years no wood whatever was formed in the fragment under examination. The 

 varying width of zones results from the age of the tree ;, so that it is less as the tree 

 advances in life, as also from the interruption to growth, which not unfrequently 

 continues on one side of a plant throughout a greater part of the growing season. This 

 may be readily observed by noticing a section of almost any stem; for then it will be 

 evident that the pith does not occupy the geometric centre of the plant. Dr. Lindley 

 gives the measurements of two sides of four stems, which he selected from East Indian 

 trees, which exemplify this fact clearly : 



" Suppose that a portion of the smaller side in the first example were examined, the 

 observer would find that each zone is 0*225 of a line deep, and as the whole diameter 

 of the stem is 45 lines, he would estimate the side he examined to be 22 '5 lines deep, 

 consequently he would arrive by calculation at the conclusion that as his plant was one 

 year growing 0'225 of a line, it would be a hundred years in growing 22*5 lines, while 

 in fact it has been only forty years." 



Thus, whilst it is difficult to ascertain with great certainty the age of any tree when 

 a whole section can be obtained, the difficulty is vastly greater when only a fragment 

 can be examined. 



The great size of the trunk of a tree is prima facie evidence of its antiquity ; and 

 judging from that fact alone we should be disposed to admit that the following remark- 

 able trees must be very aged : 



The Chesnut pf Mount Etna (Castanea de Centi Cavalli) is 180 feet in circum- 

 ference. 



A Plane tree in Turkey, 150 feet in circumference. 



Some of the Brazilian Hymenaeas, 84 feet in circumference. 



In respect of height, it is known that the Araucarias sometimes attain to the 

 height of more than 200 feet. 



The Pinus Darglariana of Oregon is 193 feet high ; and the Pinus Lambertiana is 

 226 feet in height. 



