62 AGE OF PLANTS. 



nutrition, even when it does not cause the /all of the leaves, as 

 ordinarily happens. 



72. In hot countries, where there is no winter properly speak- 

 ing, there are, nevertheless, periods of activity and repose in 

 plants which correspond to the dry and wet or rainy season; 

 there the great heat arrests vegetation as the cold does in our 

 climate, and the life of plants is reanimated in the rainy season. 



73. As we have already stated, a great number of plants are 

 annual, that is, they live only through one year ; others com- 

 plete their growth only in the second year, and die on the 

 approach of the second winter, and are termed biennial ; others 

 again continue to live many years, and are for this reason called 

 perennial plants. All herbaceous plants are annual or biennial; 

 ligneous plants live many years, and the duration of their lives 

 exceeds every thing we could imagine. One of the orange trees 

 at Versailles, in France, appears to be nearly four hundred 

 years old; and a tree of the same species, which* may be still 

 seen at the convent of Saint Sabin in Rome, was planted there 

 by Saint Dominick more than six hundred years ago. In Swit- 

 zerland there are linden trees which, to judge from their diameter 

 and the manner in which these trees ordinarily grow, ought to be 

 more than a thousand years old ; and there is a chestnut tree at 

 Sancerre, which was known six hundred years ago as the great 

 chestnut, from which we may conclude that its age is not much 

 less than that of the lindens we have just mentioned. But the 

 tree most celebrated on account of its longevity is, unquestion- 

 ably, the baobab, that flourishes in Senegal. A botanist named 

 Adanson notices one which three centuries before had been 

 observed by two English travellers, and on excavating the trunk 

 of this tree, there was found an inscription they had written, 

 covered by three hundred ligneous layers; from this they were 

 enabled to judge how much this gigantic plant had grown in three 

 hundred years, and, comparing this with the diameter of the tree, 

 it was estimated that the probable duration of its existence wag 

 upwards of five thousand years. 



72. Is there any variation in the activity of the functions of vegetables 

 in hot countries ? 



73. What is meant by an annual plant ? What is meant by a biennial 

 plant? What is a perennial plant? What is supposed to be the age of 

 the oldest living tree ? 



