the Age of Trees from the number of Eings. 455 



pspudoacacia have a shorter repose ; and that the Acacias, 

 natives of the still hotter Australia, only rest for a few 

 weeks, in some seasons perhaps not at all. Thus each 

 species appears to follow the practice of its ancestors, 

 although all are now living under the same atmospheric 

 conditions. 



In conclusion, I may point out the desirability of making 

 some distinction between the annual growth of wood and 

 the line of demarcation between two annual growths. It is 

 true the latter is a vague element which cannot be easily 

 defined. Still it is often of practical utility in ordinary 

 speech. Perhaps the annual growth might be called a zQiic, 

 and the line of demarcation a ring. 



EXPLANATIOX OF PLATE IV. 



Fig. 1. Surface of a section of a stem of Acacia mollissima, 6| 

 years old. Natural size. The line of demarcation between the 6th 

 and 7th year's growth is pretty strongly indicated to show its 

 position, but is very feebly marked on the block, as shown in the 

 finished part of the drawing. It is also very feebly marked micro- 

 scopically. 



Fig. 2. Junction of the 4th and .5th year's growth. Transverse 

 section. Illustrates the structure of a true ring, x 600'. (a) -ith 

 year's wood ; (b.) 5th year's wood. 



Fig. 3. Junction of the 1st and 2ud year's growth. Transverse 

 section. Illustrates a less strongly marked true ring. Bounded on 

 each side by a medullary ray, x -1:00\ («) 1st year's wood ; 

 (6) 2nd year's wood. 



Fig. 4. Transverse section of a false ring, between the 2nd and 

 3rd true rings, x 400', (a.) older wood; (6) younger wood. 

 Bounded on each side by a medullary ray. 



