550 Rivdt. — -The Anatomy of Rhododendron ponticum , L. 
Ia comparing the values for the number of water-conducting elements 
per sq. mm. we have the following : 
Rhododendron 
Holly . 
Hazel . 
Ash 
556-1908 
33I-II95 
1 1 5-4000 
32-633 
From this little can be deduced except that the extreme figures for 
hazel cannot be representative of any great length of the stem, because, 
although the average cross-area of its water- conducting elements reaches 
a higher maximum than in rhododendron, and although the figure for the 
maximum number of conducting elements is extremely high, yet the 
values for the C curve fall lower than they do for rhododendron. Obviously 
the balance between size and number for securing maximum conductivity 
is very delicate and is achieved in hazel rather than in rhododendron, but 
in the end we are forced to conclude that it is the length of the vessels 
rather than this balance which is the important factor in conductivity. 
Conclusion. 
The results obtained from the quantitative analysis of the wood in 
Rhododendron ponticum and the holly have been described and correlated 
with the results given by experiments on their specific conductivity. An 
attempt has also been made to compare the ascertained data with those 
given elsewhere for the stool shoots of hazel and ash. The comparison 
indicates that the evergreen shrubs examined have, as a characteristic of 
their wood, vessels of a smaller bore and shorter length than those of the 
deciduous hazel and ash. At the same time all four agree in the fact that 
there is a general decrease in absolute conductivity from the base upwards 
in each year’s growth, while there is an increase in specific conductivity 
from the base up to a point near the apex of each years growth. 
In conclusion I wish to express my thanks to Professor Farmer both 
for the suggestion of this research and for the assistance which he has 
rendered. 
