450 Dr David Christison on ascertaining 



some of their chief characteristics, together with the dura- 

 tion of the seasonal-growth of the species to wliich they 

 belong, from monthly girth-measurements of other trees of 

 their species taken for several years by Mr Hall. 



Rohinia pseudoacacia, Lin. — Age, ten years ; annual girth- 

 increase of the specimen, 1| inch ; winter sleep of the species, 

 six to eight months, during part of which, however, there 

 was a very slight growth. 



Melia azedaracli. — Native of Syria, but naturalised in South 

 Europe (Lind.) ; a favourite boulevard tree in Spanish South 

 American cities, there called " Paraiso." Age, eleven years ; 

 annual girth-increase of the specimen, 2*27 inches ; growth 

 ceased, or was greatly retarded in the species for from four 

 to six months annually ; in 1888, after a good start in 

 August, the rate fell greatly in September and October. 



Acacia dcalbata v. mollissima, Willd. — Evergreen ; native 

 of Australia. Age, seven years ; annual girth-increase of 

 specimen, 1"97, but that of two other of the species was 5 

 inches ; growth of the species pretty steady through the year, 

 except a total cessation from 12th February to 12th March 

 in 1886, from 12th December to 12th January in 1886-87, 

 and from 12th January to 12th February 1888. 



Acacia mclanoxylon, E. Br. — Black wattle ; native of Aus- 

 tralia, Age, eight years ; annual girth-increase of the 

 specimen, 3 5- inches ; growth of the species much retarded 

 for two to three winter months in 1886 and 1887, and 

 ceased entirely for two months in 1888. 



Acacia lophantka, Willd. — Deciduous ; native of Australia. 

 Age, five years ; annual girth-increase of the specimen, 4 

 inches ; growth of the species unknown. 



Before proceeding to describe the rings in these sections, 

 it will be well briefly to recall the characteristics of rings in 

 hardwood trees of temperate climates. 



1. Perhaps the most invariable differentiating character is 

 the difference in density between the spring and autumn 

 wood, the former being much looser in texture than the 

 latter. This is very evident under the microscope, but often 

 shows a marked distinction to the naked eye also. 



2. At the outer side of the autumn wood there is usually, as 

 it were, a rather sudden and extreme compression or flattening 

 of the tissue, as seen under the microscope, which forms the 



