Delf . — Transpiration in Succulent Plants . 431 
In a typical experiment with Sedum spectabile six similar shoots were chosen, 
with as nearly as possible the same number of leaves. On June 30 the ten 
oldest leaves of three shoots were detached and weighed ; no account was 
taken of the cut surface where the leaf had been attached, since this is un- 
usually small in species of Sedum. The detached leaves were left to dry 
on blotting-paper, together with the remaining three shoots, the fresh weight 
of which was also found. On July 10 the six lowest leaves of the shoot 
were quite dry ; the detached leaves were withered, but less so than those on 
the plant. The weight of each set of leaves was again taken, and the initial 
weight of the cut leaves was calculated in terms of an equal weight of the 
shoots with attached leaves. The results are shown in the following table, 
taken from Pringsheim’s paper : 
Table IX. 
Leaves of Sedum spectabile , 
Detached Leaves. All io leaves. 
withering. 
Lozvest 6 leaves. 
Upper 4 leaves. 
a. Initial wt. June 20 
7.92 grm. 
4.29 grm. 
3.71 grm. 
b. Wt. July 10 
5*23 „ 
2 -74 „ 
2-49 „ 
c. Loss % fresh wt. 
33*9 » 
3^-1 „ 
32-9 „ 
'. Attached Leaves. 
d. Wt. July 10 
1.64 „ 
0.165 „ 
1 ‘45 >> 
e. Loss % fresh wt. 
79-5 „ 
96*3 » 
60.9 „ 
f. Transport of water % fresh wt. 
45-6 „ 
60.2 ,, 
27 
g. Transport % of Total Loss 
57 -i >> 
62-5 „ 
46 
From these figures Pringsheim concludes that the water loss of individual 
leaves on the plant is greater than when detached, and that the greater 
part of this water loss is due to displacement within the plant. Very similar 
results were obtained from experiments with the most varied type of plant, 
such as Bryophyllum , Cotyledon^ Mesembryanthemum , Trade sc antia, Rhip- 
salis , Sambucus , and Vicia. 
Not less interesting are the observations made by Pringsheim on the 
osmotic conditions within the same plants, both normally and when wither- 
ing. It was found that, with very few exceptions, the older leaves had 
a lower osmotic pressure than the upper ; for example, in leaves of Sedum 
spectabile , the osmotic equivalent expressed in terms of a standard 10 per 
cent, solution of potassium nitrate was found to be— for leaves 
5-5J cm. long (oldest) 18-30 per cent. 
3 „ „ (younger) 34-36 „ „ 
^“•^2 >> 5 ) 5 ) 3 ° ” >> 
^2 >> >> >) 3 ^ » ” 
The osmotic equivalent was thus greatest at the growing point, falling off 
quickly and remaining fairly constant for the adult leaves. 
