200 De Candolles Essay [April, 



at certain intervals would shew the law of increase in the diameter of old trees, 

 and compared with other measures, would afford approximate means for estimating 

 their age. Thus we find from Evelyn that there existed in 1660, an immense oak at 

 Welbeck-lane, which was 33 feet 1 inch in circumference, (nearly 11 feet diameter) ; 

 this same oak, though mutilated, still existed in 1775, and had a diameter of 12 feet . 

 it had grown 12.6 in. in 120 years, a little more than a tenth of an inch yearly. From 

 whence it may be concluded, that the law of increase, indicated by the oak in my 

 table which was 333 years old, holds nearly good for a tree of much greater age : 

 therefore, if the oak of Welbeck-lane be calculated by the tabular data of the oak of 

 333 years, it will be found that, in Evelyn's time, it must have been nearly 1300 

 years old; and more than 1400 years old, in 1775. 



5. Finally, in cases where it is impossible to obtain the transversal cut of an 

 old tree, there may be opportunities of making a slight incision on the side and 

 discovering how much it has grown in a given number of years, and thus provid- 

 ing a minimum of its mean growth. This is the method by which Adanson dis- 

 covered the age of the Boababs. He saw how much these trees had grown in three 

 centuries, and knowing at the same time the growth of young trees, he was able, by 

 an average, to estimate the general law. The age of the Taxodium of Chapultepec 

 in Mexico might be examined in the same way. 



By following out the five methods indicated above, either separately or unitedly, 

 the age of old exogenous trees maybe ascertained in a manner which will sufficiently 

 answer the subject of this inquiry. Let us now point out the trees to which our 

 attention ought principally to be directed. The greatest longevity in the vegetable 

 kingdom ought to be found, 1st, in trees which by their hardness, their incapacity 

 of decay, or their size, are the best able to resist destructive agents ; 2nd, in countries 

 which are not liable to frost or to other causes which too frequently tend to kill large 

 vegetables. 



Among European trees, we may mention the following examples : 



1st. The young Elm, as is known, grows to a large size ; but its growth is tolerably 

 rapid. The particular one which I have marked in the table above grew near the town 

 of Morges: the observation of its layers, and the account of its fall, was kindly com- 

 municated to me by Mr. Alexis Forel ; its section shewed it to be 335 years old ; 

 it was at the period of its fall perfectly healthy, and had grown in a humid and 

 light soil: its stem was 17 feet 7 inches in diameter at the neck, 30 feet cir- 

 cumference below the spring of the branches, at 12 feet from the ground ; and 

 one of the fine large branches attained 16 feet in circumference ; the tree fell in 

 fine weather, the soil having been probably injured by the waters of Lake Leman. 

 It had grown at an average 0.3 in. a year, but if the period be divided into cen- 

 turies, it will appear that it grew .33 a year during the first century, .23 during the 

 second, and .25 during the third ; these calculations accord with those which are 

 generally afforded by young elms planted in front of the French churches by order 

 of Sully. It is important to distinguish the progress of increase in elms with 

 large from the rate in those ivith small leaves ; the latter are most long-lived and 

 appear to grow more slowly. 



2nd. I saw in 1814, at Gigean, near Montpellier, an Ivy tree the stem of which near 

 the ground was six feet in circumference, and which attracted attention by its extra- 

 ordinary size. Another ivy, 45 years old, was only 7§ inches in circumference. Were 

 this to be taken as an example, the ivy at Gigean must have been 433 years old in 

 1814, and must now be about 450 years old, if as I hope, it still exists ; it is pro- 



