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tree-like trunk or stem, build this up in course of time by 

 an accumulation of the basal parts of the fronds, which, 

 for an inch or two, persist, although the rest of the frond 

 perishes, and, as a rule, only retains vitality for one season, 

 when it is replaced by a new frond, the old one drooping 

 and withering, and eventually decaying completely, leaving, 

 however, behind it the portions referred to as a permanent 

 contribution to the trunk. The elevation of the trunk is 

 due to the fact that each year the growing point, from 

 which the fronds spring, stands at a little higher level, so 

 that each circle of fronds is somewhat higher than the 

 preceding one, and consequently, in course of time, a trunk 

 of very considerable altitude may result. 



It is this increase which eventually determines the 

 length of life, as it obviously must, in time, increase the 

 risk of toppling over. This risk, however, is lessened by 

 the fact that however lofty the trunk, the fronds at its 

 summit are fed mainly, or entirely, by fresh roots which 

 issue from their bases, each one producing a bundle of its 

 own. These roots creep downwards between the old frond 

 bases, forming the mass of the trunk, and strengthen it 

 greatly as they proceed, until, in the moist and humid 

 atmosphere which is an essential condition of such growths, 

 they may actually reach the ground. 



It will be seen by this that a fern trunk is essentially 

 different in structure from an ordinary tree trunk, since it 

 forms no bark, and is not increased in diameter by an annual 

 internal ring of new wood, which in a tree constantly 

 strengthens the trunk to withstand the increasing strain of 

 the ever wider and wider extension of the system of 

 branches it has to bear. Unassisted, therefore, it is clear 

 that the duration of life of a Tree-fern is determined, 

 finally, by the power of the rising stem or trunk to support 

 the heavy weight of the circle of fronds at its summit, and 

 it is therefore as impossible to imagine a longevity even 

 approaching that of many trees proper as it is to imagine 



