g 6 Ewart and Rees .— Transpiration and the Ascent of 
Acacia mollissima ( continued ):— 
. Diameter 
A S e - at base. 
Positioti of 
Leiigth of 
Dia 77 ieter of 
lo 7 ?gest vessel. 
longest vessel. 
largest vessel. 
(f) Branch of same 2 yrs. i-6 cm. 
New wood 
121 cm., 17 vessels 
.098 mm. 
Length 1-25 m. 
at 74 cm. 
Average no. 
of vessels at tip (24 per sq. mm.), 8 
31 
Acacia Lophantha: 
Branch 1 yr. 1 cm. 
40 cm., 29 vessels 
.12 mm. 
at 22 cm. 
Average no. 
of vessels at base (13 per sq. mm.), 
1021 
A verage 
Dici 7 neter 
of vessels . 
•07 mm. 
• 08 mm. 
Very similar results were given by young trees of Eucalyptus , except 
that there was an even more marked difference in the appearance of the 
wood from the trunk and branches, the vessels of the latter being much 
smaller in diameter and much more numerous per sq. centimetre. The fact 
that one or two vessels out of several thousand may run nearly the whole 
length of the tree, and only a small percentage one-third to half the length 
of the tree, the great majority being very much shorter than this, is some¬ 
what suggestive. It may be that these few very long vessels are specially 
adapted to convey continuous columns of water with ease and rapidity, but 
that since a single bubble or plug of gum may throw the whole tube out of 
action more or less completely, the plant prefers to rely for everyday use 
on the more numerous much shorter vessels, where the blocking of single 
vessels is less serious. On the other hand, the formation of these single 
vessels of great length may be more or less the result of accident, or at 
least not a fact of any special functional significance. 
Mercury Method. 
I. Eucalyptus macidata var. citriodora: 
, Diameter Position of 
6 ’ at base. longest vessel. 
Length of 
longest vessel. 
(a) 
(*) 
Branch 
Branch 
6-8 yrs. 2.1cm. 
6 yrs. 2-5 cm. 
(0 
Branch 
Newest wood 25 at 96 cm. 
New wood 119 cm., 19 vessels 
at 78 cm. 
Average no. of vessels in stem, 9,500 
3rdyr’s.wood 105.5 cm., 22 ves¬ 
sels at 85 cm. 
Average no. of vessels in stem, 8,835 
4 yrs. 1.5 cm 
II. Eucalyptus viminalis: 
Diameter of 
largest vessel. 
• 145 mm. 
.076 mm. 
•084 mm. 
Average 
Diameter 
of vessels. 
.093 mm. 
•054 mm. 
•065 mm. 
Forked tree. 
Height 2-51 m. 
Fork A. 
6 yrs. 
4-5 cm. 
In new wood 
198 cm., 9 vessels 
.091 mm. 
•062 mm. 
Fork B. 
6 yrs. 
4.4 cm. 
In new wood 
at 147 cm. 
199-3 cm., 4 vessels 
•091 mm. 
•062 mm. 
Branch of same 
Root and 
3 yrs. 
6 yrs. 
1.4 cm. 
Root, 
In new wood 
at 195 cm. 
5 vessels at 90 cm. 
17 vessels at 62 cm. 
• 118 mm. 
.082 mm. 
hypocotyl 
2-5 cm., 
Hypo., 
12 cm. 
from its position, 
the longest vessel probably extended from root through main 
axis. Length about 316 cm. 
