182 LEAVES FROM THE BOOK OF NATURE. 



number of years is usually ascertained since the well- 

 known author Michael Montaigne first started this theory 

 by counting the concentric rings. Care must, however, 

 be had not to forget, that some trees begin to form these 

 only after several years' growth, and that, whilst northern 

 trees shed their leaves but once a year, and therefore add 

 but one ring during that time, those of the tropics change 

 their foliage twice or thrice a year, and form as many 

 rings. This renders the age of such trees, as were here- 

 tofore considered the oldest, somewhat doubtful ; still there 

 are some remarkable cases of longevity well authenticated. 

 Humboldt measured a gigantic dragon-tree near the peak 

 of Teneriffe, and found it possessed of the 'same colossal 

 size, forty-eight feet round, which had amazed the French 

 adventurers, who discovered that beautiful island more than 

 three centuries ago and yet it still flourished in perpetual 

 youth, bearing blossoms and fruit with undiminished vigor ! 

 Some yew trees of England, and one or two oaks, claim 

 an age of from one thousand four hundred to three thou- 

 sand years, and would, if their claims were substantiated, 

 be the oldest trees in Europe but a famous baobab, on 

 the banks of the Senegal, is believed to be more than 

 six thousand years old, in which case its seed might have 

 vegetated before the foot of man trod the earth ! Its only 

 rival is a cypress tree in the garden of Chapultepec, which 

 Humboldt considers still older ; it had already reached a 

 great age in the days of Montezuma. A curious old age 

 is that of a rose-bush which grows in the crypt of the 

 cathedral of Hildesheim, in Germany ; it was there planted 

 by the first founder of the church, and is expressly men- 



