LETTER XI. 



Ill 



them." The remains of the seedhng oak-plant would 

 be inadequate to support the whole growth of the 

 oak-tree's twenty-first year. But it is quite equal to 

 that of the second year, as the remains of the twentieth 

 are to the twenty-first, — the growth of each year being 

 exactly proportioned to that of the years immediately 

 preceding and following it, — to the support it has to 

 rest upon, and to the burden which in its turn it has 

 to bear. 



10. I will now introduce you to M. Mirbel, a bota- 

 nist deservedly of great celebrity, with whose views 

 on the subject before us I only became acquainted 

 (and that by the merest chance) several years after 

 my own had been made public. They are contained, 

 in as far as known to me, in a paper in the fourth 

 volume of the Quarterly Journal of Science, entitled 

 " Of the Death of Plants : From the French of M. C. 

 F. Brisseau Mirbel." In reading what I shall here 

 quote from that paper, you will not fail, I think, to be 

 struck with the very close resemblance which his views 

 generally and many of his expressions bear to mine. 

 JN'or can I forbear expressing my surprise that views 

 so detailed, and so clearly and forcibly set forth by 

 M. Mirbel, should not have found their way into our 

 systematic works on vegetable physiology. 



11. M. Mirbel begins by observing, that 



" Plants, like animals, unless destroyed by disease or casual- 

 ties, are doomed to die of old age.^'' 



