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



The value for the wood of the Yew {Taxus) was also low, but slightly 

 higher than that of Holly, with specific conductivity of 12 + 2 in the rather 

 small number (6) of twigs examined, but the ages of these ranged from three 

 to eight years, and I think the result may be taken as fairly accurate. 

 Podocarpus Milanjiana grown in a plant-house in the Physic Garden at 

 Chelsea was also examined. The plant was a well-grown one, and the 

 branches were each divided into a basal and apical half. The average of the 

 specific value of each pair thus obtained was also strikingly uniform, and it 

 illustrates the desirabilit)^ in work of this kind, of getting fair averages to use 

 as a basis of comparison. There are often considerable fluctuations in the 

 conductibility of different regions of lateral branches, but when the average 

 of the whole length is taken a figure is reached which is very near the mean 

 for the particular species. This is much more obvious in deciduous than in 

 evergreen trees, as in the former the fluctuation is considerably greater. It 

 will be seen that in eight branches of Podocar.pus the mean is 9'3 with an 

 extreme variation of only I'l if the weak fourth shoot (at 7'1) be omitted. 

 The Pine {P. sylvestris) and Larch (L. europoeus) presented diflficulties, owing 

 to the' presence of resin, but the figure for their specific conductivity is 

 respectively about 14 and 16. Such uniformity as that indicated for the 

 species hitherto mentioned is by no means universal even in the evergreens. 

 Thus 15 stems of Garreya elliptica, with an average of 14"6, showed a 



Table III. — Podocarpus Milanjiana. Each branch is divided into a basal (L) 

 and an apical (U) half, and the results of each pair are bracketed. 



Order of 

 segment. 



Age in 

 years. 



Absolute vol. in c.c. 

 per 5 hour. 



Specific vol. in c.c. 

 per 5 hour. 



Averages. 



L 

 U 



3 

 3 



0-9 

 0-7 



8- 8 "1 



9- J 



= 8-90 



L 

 U 



5 

 5 



1-4 

 1-4 



8-9 1 

 10-4 J 



= 9-65 



L 



7 



2-0 



10-3 1 



= 9-65 



TJ 



4 



1 1 



9-0 ; 



L 

 U 



4 

 4 



0-7 

 0-5 



7-2 1 

 7-0 / 



= 7-10 



L 

 TJ 



4 

 4 



1 -8 

 1-2 ■ 



9-9 1 

 7-2 1 



= 8-55 



L 



4 



1 -2 



9-2 1 



= 10 -35 



U 



4 



1 -3 



11 -5 J 



L 

 U 



6 

 5 



3-4 

 3-2 



9-9 1 

 10-7 / 



= 10 -30 



L 

 U 



4 

 4 



1-0 

 0-9 



8-9 1 

 10-5 J 



= 9-70 





74-10 

 = 9-27 



