THE AUSTRALIAN GREY MANGROVE. 279 



about fit the space now left, judging from the dimensions 

 of an original shield. 



Conclusions. 



Reviewing some of Mr. Lushing ton's theories (supra) of 

 the remarkable growth of this tree, my investigations 

 show (a) that forest fires do not play the part he assigns 

 to them, and that the break of concentricity is not due to 

 that cause, as fires are not known to have occurred where 

 the trees abound, and yet breaks occur in the ring, and 

 then the stems are so regularly built up by these rings that 

 traces of retardation of growth are rarely perceptible, such 

 as one finds in other trees that have suffered from artificial 

 or natural causes. My correspondent, who has watched 

 hundreds of trees for many years, dismisses this theory as 

 applied to New South Wales trees, as bush fires rarely if 

 ever occur amongst them, and my own personal examination 

 of the trees in this and other districts does not support this 

 theory. It is in the fifth or sixth year of the age of the 

 tree that these breaks in the rings begin to develop. 



(b) Neither is there evidence forthcoming to support this 

 gentleman's suggestion that each ring or portion of a ring 

 represents a tide, if I understand his idea rightly, for during 

 the known age of certain trees, far more tides must have 

 passed round the tree than are represented by the rings. 

 Sections were made from a tree planted seven years ago, 

 and the number of rings correspond to this number, and 

 (c) Mr. Lushington's experiment of finding the number of 

 spurious rings to correspond to the number of months proves 

 that the growth of trees must be very much faster in 

 India than in Australia, for the data given above under the 

 seven years old trees are indisputable. 



Finally, I can only say that after giving much thought 

 and attention to the subject, I am unable to advance any 

 definite explanation to account for this remarkable struc- 



