Ilex Aquifolium , L ., zW Reference to Specific Conductivity. 539 
Curve C (percentage of the wood occupied by the cavities of water- 
conducting elements). This curve illustrates, as far as is possible from the 
consideration of transverse sections, the anatomical basis of the variations 
in the water-conducting powers of the wood, and thus is to be correlated 
with the specific conductivity — i. e. with the volume of water transmitted 
by a length of 15 cm. per 1 sq. mm. of wood as seen in transverse section. 
There are considerable differences in the curves exhibited by the one-year- 
old shoots of Rhododendron ponticum and the three- or four-year-old shoots 
of holly, but in general the curves rise from the base and fall away again 
to the apex. In rhododendron the curves may be described and explained 
as follows : The steep rise from the base through the lower internodes 
