262 Holmes. — A Contribution to the Study of 
for the successive first-year segments of the same specimen. In general, 
there appears to be a similar tendency towards a rise followed by a fall, as 
was shown for Hazel and Ash. That is, there is a preponderance of fibrous 
elements towards the base of the shoot, where mechanical efficiency is most 
necessary, while at the apex the specific conductivity is again reduced owing 
to the small size of the conducting elements, in spite of their large number. 
Exceptions to this occurrence of rise and fall in Curve C for first-year shoots 
are shown in S 1916, a short basal main stem, in which there is a rise 
only; and in S$c, a very weak lateral in which there is only a fall, 
cf. A 8 e. 
Wood of the second and following years . We come now to the con- 
sideration of the character of the wood in parts of the stem more than one 
year old, apart from that composing the innermost annual ring. In the 
second and later annual rings leaf-trace bundles are absent, so that the wood 
has a more uniform structure ; the vessels also reach a greater diameter. 
The differences between the wood of the first and subsequent years are 
illustrated in Figs. 4 and 5, in which lines, representing the characters of each 
annual ring separately, are drawn for S3, the five-year-old specimen. The 
transverse sectional area of the wood composing each annual ring, Curve A, 
Fig. 5, is maintained at a fairly constant level in the internodes as its course 
