Mar. 1892.] THE BOTANICAL SOCIETV OF EJ)1XBURGII, 317 



specimens of rrumis Fadus, Pi/nis Aumparia, and Carjnnus 

 Bdulus are far apart, but it is to be presumed their conduct 

 is due to exceptional causes. 



It will be observed that equilibrium is established as high 

 as the thirteenth and fourteenth trees in the list. Hence 

 only twelve of the fifty-eight grew chiefly in the first period, 

 and no less than forty-four chiefly in the last period. But 

 as some species are much more largely represented than 

 others, it is of consequence to ascertain the averages for the 

 apccies, nwd I shall take the old and young groups separately, 

 as the latter is more reliable than the former. 



In the younger group (Table IX.) three species increased 

 mainly in the first period ; in three the proportions were equal ; 

 and in thirteen the increase was chiefly in the last period. 



Table IX. Proportional Increase in Girth in Deciduous 

 Species in the First and Second Half op the Growing 

 Season (Young Group). 



Should it be necessary to take about a week of June from 

 the second period and add it to the first, in order to make 

 the two growing periods actually equal, the number of 

 species on either side of equilibrium would probably be 

 about the same. The extremes are — Fraxiiius, 69, 31, and 

 Tilia^ 67, 33, against Populus fastigiata 30, 70, and Quercus 

 Mobur, 35, 65. 



In the older group (Table IX.) the preference for the 



