Water -Conductivity of the Wood in Trees and Shrubs. 243 



transmitted through 15-cm. lengths of the stems at the places indicated, 

 under the same standard conditions of pressure, etc., as have been main- 

 tained throughout the enquiry. The figures opposite, which are not so 

 enclosed, give the specific conductivity values. It is thus seen to be almost 



Fig. 2.~ Semi-diagrammatic sketch of the top of a young Aah tree. The figures in 

 brackets denote absolute volumes of water transmitted, those adjacent to them 

 denote the specific volumes, at the corresponding places. 



inevitable that the apex should die back, and that one or more of the stronger 

 shoots should assume the role of leaders. The shoots further behind may 

 grow out also, but they often fail to do so unless the stem be cut back. Of 

 course it is not suggested that this water-conductivity factor is the only 

 one that determines total habit ; on the contrary, the final result is certainly 

 made up of a complex of factors. But it seems clear that it does constitute 

 an important element in determining which may and which may not become 

 dominant shoots and branches. 



In fig. 3 the top of a vigorous young Sycamore tree is represented for 

 comparison with the Ash. It becomes at once obvious, on the basis of the 



