242 Prof. J. B. Farmer. On the Quantitative Differences in the 



Table VIII. — Two Long Stool-shoots of Hazel, A and B, cut into Lengths 



from Base to Apex. 



Shoot. 



Order of 



Age in 



Absolute Tol. 



Specific vol. 





length. 



years. 



in c.c. per i hour. 



in c.c. per \ hour. 



A 



Basal 



3 



37 -6 



45 -0 





2 



3 



32 -0 



48 -0 





3 



3 



22-6 



48-5 





4 



2 



12 -8 



38 -0 





5 



1 



7 -8 



35 -5 





6 



1 



5-0 



37-5 





Apical 



1 



2-2 



35 -5 





Total 





288-0 





Average 





= 41-1 











B 



Basal 



2 



27 -e. 



44-5 





2 



2 



20-8 



47-5 





3 



2 



14-2 



40-5 





4 



1 



3-8 



25 -5 





Apical 



1 



2-4 



23 -7 





Total 





181 -7 









= 36 -3 



thickening occurs, the absolute conductivity of course undergoes a corre- 

 sponding increase. 



But the absolute as well as the specific conductivity of the wood falls off 

 very rapidly as the apical region both of the leader and the lateral branch is 

 approached. It is, I think, a fair inference that this falling off in conduct- 

 ing efficiency is responsible for the very characteristic habit of growth of 

 young Ash trees and coppice-shoots. The apex often dies back for a con- 

 siderable distance each year, and the elongation of the stem is assured by one 

 or more of the stronger lateral shoots. More or less equally forked tops are 

 not uncommon during the late spring and early summer, but one of the 

 branches of the fork usually obtains the lead, and it is always found that its 

 success is correlated with superior specific conductivity. A large number 

 of examples have been employed to test these peculiarities in the Ash, 

 as regards water-conductivity, and no exception has been encountered. 

 Probably the best way of rendering the position clear will be found in pre- 

 senting, in semi-diagrammatic form, the results obtained in a typical instance. 

 The diagram illustrates the mode of branching, as shown in a vigorous young 

 Ash tree growing in a hedgerow, and cut off in the early spring of 1917. 

 The figures enclosed in brackets represent the absolute amount of water 



