Water-Conductivity of the Wood in Trees and Shrubs. 233 



Table I. 



Euonymus jcvponica (Evergreen). Euonymus europceus (Deciduous). 



Age in 

 years. 



Absolute vol. in 

 c.c. per i hour. 



Specific vol. in 

 c.c. per J hour. 



Age in 

 years. 



Absolute vol. in 

 c.c. per i hour. 



Specific vol. in 

 c.c. per 5 hour. 



1 



0-6 



12 -5 



2 



10 -6 



29 -7 



1 



0-5 



7-5 



5 



6-0 



31 -0 



1 



0-5 



10 -2 



2 



16 -0 



38 -0 



2 



1 -4 



9-0 



6 



12-2 



46-3 



2 



1 -0 



8-9 



4 



16 -4 



48-3 



1 



0-6 



9-5 



6 



8-6 



51 -0 



1 



-4 



8-6 



5 



13 -8 



45 -5 



1 



1 -4 



13 -4 



3 



7-8 



47-3 



2 



0-7 



11-6 



5 



11 -4 



45 -0 



2 



0-8 



11 -3 



3 



5-2 



39-5 



1 



0-8 





4 



21 -0 



DO U 



1 



0-6 



10-9 



5 



4-8 



26 -7 



1 



0-3 



9-8 



2 



9-8 



37-0 



2 



5-2 



19 -1 



4 



8-8 



40-0 



3 



4-2 



17-0 



2 



9-0 



29-7 



2 



3-9 



17-1 



2 



14-4 



37-0 



3 



3 1 



14-9 



2 



10 -2 



33 -0 



1 



1 -5 



13-7 



3 



8-8 



45 -5 



Total 



Average 



218 -4 

 = 12-1 



Total 



! 



723 -5 

 = 40-2 



A second feature which is brought out in the Table is that the range of 

 actual values is larger in the deciduous trees. This is largely owing to the 

 fact that the proportional range is not very dissimilar as between the two 

 classes as a whole. But the relatively high mean in the deciduous plants 

 makes the fluctuation more noticeable, and its absolute extent is, of course, 

 much greater. This feature is evidently bound up with the water supplies 

 at the disposal of the more rapidly transpiring leaves, but the inter- 

 relations of water supply and transpiration are very complex, and will not 

 be further discussed here, especially as they are forming the subject of 

 separate research at the present time. 



Nevertheless, the opinion may safely be hazarded that the relatively 

 efl&cient character of their wood, together with its plasticity in relation to 

 requirements, constitute, at any rate, two of the factors which have 

 co-operated to enable the deciduous trees to assume the dominant position 

 they enjoy in the ordinary environment within the temperate zones. Even 

 within the tropics deciduous species are not uncommon, especially where 

 there is an alternation of dry and rainy seasons. 



The plasticity in wood-structure is borne out even within the limits of 

 individual shoots, especially in the free-growing " extension " branches. 

 The specific conductivity is often lower at the base than higher up, in which 



VOL. xc. — B. u 



