H. BOTANY AND HORTICULTURE. 347 



H. BOTANY AND HORTICULTURE. 



TREE GROWTH AND THE PRESSURE OF THE BARK. 



The influence of the pressure of the bark upon the struct- 

 ure of the annual layers of woody fibre has formed the sub- 

 ject of an excellent memoir by De Vries, who states that 

 while the classic work of Nordbinger (i>er Ilolzring, etc., 

 1870) gives a complete resume of our knowledge with re- 

 spect to the connection between the thickness of the an- 

 nual layers and the pressure of the bark, yet, on the other 

 hand, the phenomena connected with longitudinal incisions 

 still remain to be considered; and he has made a long series 

 of experiments at the Botanical Gardens at Amsterdam, in 

 which he first has diminished artificially the pressure of the 

 bark by longitudinal incisions ; and, second, has increased 

 the pressure artificially by enveloping the tree wdth a tight 

 cord. He has been able to demonstrate, first, that the radial 

 diameter of the woody fibres depends upon the pressure ex- 

 erted by the bark during their formation ; the greater the 

 pressure the smaller the radii of the fibre. Second, the 

 number and the size of the vessels which exist in any 

 woody shell depends upon the pressure exerted by the 

 bark during the formation of the shell : to a greater press- 

 ure corresponds a smaller number and a smaller diameter of 

 the vessels. 1 E^ XL, I. 



THE ELM OP BOSTON COMMON. 



Li the Transactions of the Massachusetts Horticultural So- 

 ciety for the year 1876, some interesting remarks are pub- 

 lished, made on the occasion of the prostration by a gale of 

 the ancient elm on Boston Common, which event occurred 

 on the 15th of February. Mr. Hovey stated that one of the 

 only two living seedlings of the Charter Oak, and which w-as 

 now forty years old, was at present standing on his own 

 grounds at Cambridge. Mr. Wilder suggests that a young 

 tree growing very near the roots of the great elm was j^rob- 

 ably either a seedling or a sucker, and should be planted on 

 this centennial year as a successor to the old tree. Mr. 



