LETTER XI. 



113 



soon after extended in every way; in process of time their 

 membranous walls, fortified by the absorption of nutrient juices, 

 grow thicker, and lose by degrees their original pliancy. The 

 membranes once hardened, excitement ceases to be produced, 

 and the vital functions are at an end ; nourishment is no longer 

 drawn, growth is at a stand, and the plant, unable to resist 

 the ceaseless attacks of the external agents employed by nature 

 for its destruction, decays in a short time." ''By renewals of 

 the same nature, the life of shrubs and trees proceeds. In 

 them, the liber or inner bark represents the herbaceous plant, 

 and has, like that^ only a short period of vegetative existence. For 

 when vegetation revives in the woody plant on the return of 

 spring, it is. because a new liber, endowed with all the properties 

 of a young herbaceous plant (annual), has replaced, under the 

 cortex or rind, the liber of the preceding year, which has har- 

 dened and become wood." 



12. M. Mirbel next refers to certain trees notable 



for their great antiquity, ^ and then proceeds as 

 follows : — 



'' All of them, giants as they are, vegetate, as does the 



* " The yews of Surrey, which are supposed to have stood from 

 the time of Julius Ccesar, and are now two yards in diameter ; the 

 cedars on Mount Lebanon, nine yards in girth, from the measure- 

 ment of the learned Labillardiere; the fig-tree of Malabar, according 

 to Rumphius, usually from sixteen to seventeen yards round; the 

 stupendous chesnuts on Mount ^tna, one of which, Howell tells 

 us, measured seventeen yards in circumference; the ceibas of the 

 eastern coast of Africa, of such bulk and height that a single stick 

 is capable of being transformed into a pirogua, or sailing vessel, 

 of eighteen or twenty yards from stem to stern, and of three or four 

 in the waist; the boabab of Senegal of ten or twelve yards in girth, 

 and, according to the computation of Adanson, 5000 or 6000 years 

 old."— (Mirbel, Loc. Cit.) 



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