Ilex Aqnifolium , L. f in Reference to Specific Conductivity. 547 
a considerable influence on the general average of any particular transverse 
section. The highest figures are found at the base of the four-year-old 
segment of Shoot F, where they reach 300 sq. /x. For its age, however, the 
three-year-old shoot L has very large vessels, reaching an average area of 
185 sq. ijl in the middle of the three-year-old segment, which is a much 
higher figure than is found in the corresponding part of any other shoot. 
In Shoot F the curve shows the general descent slightly flattened at the 
joints and terminating rather high' up owing to the truncated apex. In 
Shoots H and K the curve falls gradually in the older segments, but 
becomes steep towards the apex. In Shoot L the curve descends more 
Diagram XVII. Internodes numbered from base to apex. (Scale, 5 internodes = 1 cm.) 
steeply, this being a young, rapidly grown specimen, where in the first 
annual ring of each year’s segment there is a marked difference between 
the higher and lower vessels. Hence, there being no modifying influence 
of the more similar averages of the outer rings, we see the rapid descent of 
the curve, which is characteristic of a one-year-old shoot. 
Curve E (number of cavities per sq. mm.). Speaking generally the curve 
shows a general rise from the base to a point near the apex. In Rhodo- 
dendron ponticum the rise is steep at the base, flattens out slightly in the 
middle, and becomes steep in the apical internodes. The flattening in the 
middle indicates a slight falling off in the general increase in number and corre- 
sponds with an ascent in Curve D, showing that in this region there are smaller 
numbers of slightly larger vessels as compared with the region immediately 
O o 2 
