Ilex Aquifolium , Z., in Reference to Specific Conductivity . 541 
is richer in vessels than the outer rings. If a mean line is drawn touching 
the maxima of successive yearly segments, it will be found to have a general 
inclination upwards to the middle of the two-year-old or one-year old 
segment. The whole range of the line lies between 7*5 and 10-5, and the 
inclination becomes less and less in the older segments. This agrees with 
Professor Farmer’s experimental results for the specific conductivity, which 
he found to vary between very small limits (9 + 2) without any divergences 
due to age. Following the curve 
in greater detail, it will be seen 
that in each year there is a rise 
from the base to the middle and a 
fall to the apex. At each yearly 
joint there are several internodes 
(between the winter-bud scales) 
where the percentage figure is re- 
latively low. In discussing Curve 
E, it will be found that this is 
due to a great decrease in the 
number of water-conducting ele- 
ments at these regions, their place 
being taken by fibres. It is a 
matter of common observation that 
twigs are hardest to break or cut 
at the yearly joints. In Shoot F 
the figure for the percentage at the 
base of the four-year-old segment 
is 7*1 and the highest is 9-5, near 
the apex of the two-year-old. The 
descent at the upper end is only 
to 5 per cent, because there is no 
one-year-old shoot developed. In 
Shoot G the percentage is 6-9 at 
the base of the five-year-old seg- 
ment and 7-9 in the middle of the 
three-year-old. The range here is seen to be slight, indicating that the 
percentage figure is not materially affected by age, once maturity is 
established. In Shoot H the yearly phases are very clearly marked and 
also the closeness between the maxima and minima in different years. 
The total range is from 6*o at the base of the three-year-old segment to 
io-o in the middle of the two-year-old. Shoot K, the longest and stoutest 
of the set, is the richest in conducting tissue : even at the yearly joints, the 
percentage does not fall below 6-o and it rises to 11-3 in the middle of the 
three-year-old segment. This is due to large numbers of vessels and not 
to apex. (Scale, 5 internodes = 1 cm.) 
