The Water Relations of the Pine and the Silver Tree. 
11 
b. Bate of Transpiration. — In the experiments on transpiration two 
objects were kept in view, viz. : 
(1) A comparison of the rate of transpiration of similar twigs of the 
Pine and Silver Tree under the same conditions. 
(2) The relation, if any exists, between transpiration and water-conducting 
power of twigs of the same tree. 
With regard to the first of these, all the experiments showed a much 
higher rate of transpiration both per twig and per unit area of leaf surface 
in the case of the Pine than of the Silver Tree. In view of the difference in 
water-conducting power of the wood this result seemed very surprising, but 
it was obtained under various sets of conditions, e.g. in the laboratory, and 
on the roof of the laboratory, on both dull and bright days. Table II gives 
the actual transpiration per twig and per unit area of leaf surface of those 
twigs, the transpiration of which was measured under similar conditions. 
Table II. — Transpiration in grammes per hour of Pine and Silver Tree 
under similar conditions. 
(The experiments bracketed together were concurrent with one another.) 
Leucadendron. 
Pine. 
No. 
Transpiration per 
twig. 
Transpiration per 
square metre 
leaf surface. 
Transpiration per 
twig. 
Transpiration per 
square metre 
leaf surface. 
Lab. 
Roof. 
Lab. 
Roof. 
Lab. 
Roof. 
Lab. 
Roof. 
1 
2 
3 
12 
13 
14 ' 
lo) 
16 | 
17 
18J 
19) 
21) 
27 
28 
29 ' 
30 J 
10 
154 
041 
036 
094 
064 
574 
6 54 
109 
0-90 
2-05 
128 
162 
120 
2-13 
5- 95 
3 09 
364 
6- 35 
723 
22-25 
37 5 
82 
91 
13 84 
1445 
15 43 
10-07 
10-96 
62 
462 
2 26 
200 
1 60 
14-88 
7-1 
6-77 
581 
437 
447 
39 
6-62 
319 
1625 
478 
]549 
103-0 
652 
48'67 
1390 
42 32 
44-87 
355 
38-72 
In every case it will be seen that the actual transpiration per Pine twig 
is greater than that per Leucadendron twig, aod that the transpiration per 
unit leaf area of Pine is greater than that per unit leaf area of Leucadendron. 
