14 
Transactions of the Royal Society of South Africa. 
dendron of various thicknesses, but no very definite relation could be 
discovered between the rate of transpiration, and either the conductivity of 
the wood, or the area of the wood in cross section. The average of a number 
of experiments showed, however, that twigs of Leucadendron usually bear 
a larger leaf area per unit cross sectional area of wood than do those of 
the Pine. 
From the results of all the experiments described a table has been 
compiled to show the relation between the actual transpiration per 15 
minutes and the amount of water actually transmitted through 15 cm. of 
the twig in 15 minutes under the pressure of 186 cm. of water after 
injection of the wood, i. e. between the transpiration and the " standard 
transmission. 11 
Table III. — Relation between Transpiration and " Standard Transmission.'''' 
No. 
Leucadendron. 
Pine. 
Transpiration. 
Transmission. 
Transpiration. 
Transpiration. 
Transmission. 
Transpiration. 
Transmission . 
Transmission. 
2 
144 
39 
037 
3-72 
25 
1-5 
3 
130 
29 
0-45 
1-80 
1:8 
10 
137 
23 
060 
si 
250 
40 
0625 
6) 
1-28 
1-5 
085 
10, 
072 
09 
0-80 
11 f 
068 
0-6 
11 
Si 
0-27 
32 
008 
023 
10 
0-23 
14 \ 
1-69 
1-65 
10 
16 
1-45 
12 
1-2 
19, 
1-12 
05 
22 
21} 
0-41 
1-9 
0-22 
27. 
0-30 
2-7 
Oil 
28 1 
053 
30 
0-18 
29 f 
1-00 
14 
071 
30 J 
1-66 
09 
1-8 
(Concurrent experiments are bracketed together.) 
Iii every case it will be noticed that the ratio Transpiration/Transmission 
is far higher in the Pine than in the Silver Tree. This must mean that the 
Pine leaves exert a much greater suction force than do the Silver Tree 
leaves. 
IV. Discussion. 
For the purposes of discussion it will be convenient to summarise the 
outstanding results of the above experiments at this point. 
The Pine tree possesses wood of very low water-conducting power, but 
twigs, kept with their cut ends in water, show a high rate of transpiration 
