424 Delf . — Transpiration in Succulent Plants. 
water supply, and M. crystallinum transpires, as I have observed, at about 
the same rate, relative to the amount of surface, as a typical mesophytic 
plant, such as Saponaria , so that there must often be a need of water. In 
the above experiment the shoot of M. crystallinum was flaccid at first, but 
appeared to be quite turgid after five hours in water, and therefore, since 
dew often falls heavily, and lasts for longer than five hours, this plant may 
well be benefited by the absorptive power of the hairs. In M. edule , however, 
the absorption is so slight that dew formation could hardly be of value except 
in checking transpiration for the time. 
Table V. 
Absorption of Water by Transpiring Surfaces in Mesembryanthemum. 
Mesembryanthemum edule. Mesembryanthemum crystallinum. 
Ti?ne. 
Absorption % of 
Absorption % 
Absorption % of 
Absorption % 
Initial Weight. 
per hr. 
Initial Weight. 
per hr. 
5 hrs. 
0*47 
0*09 
i -7 
0.34 
23 hrs. 
2-7 
o* 1 1 
16 
0.7 
3 days 
10.7 
0.15 
27 
0.38 
Holtermann 1 asserts that the Mangroves of Ceylon appear to have the 
power of absorbing rain and dew, since the leaves were always fresh and 
turgid in the early morning after a rainless but dewy night, following a hot 
day in which they had all perceptibly flagged. However, as Burgerstein 2 
points out, this is not necessarily due to surface absorption of the dew ; it 
may simply be that the presence of the dew checks transpiration and so 
allows the water absorbed by the roots to accumulate within the plant until 
the tissues are again turgid. In those Mangroves and desert plants provided 
with salt glands the superficial absorption appears to be of real biologic 
importance, and is regarded by some as an adaptive mechanism for 
increasing the resistance of the plant to drought. 
Burgerstein , 3 who has made an exhaustive study of the whole question 
of superficial absorption of water, came to the conclusion that any part of 
the plant, whether heavily or slightly cuticularized, and whether provided 
with stomata or not, was yet capable of water absorption to some extent. 
However that may be, the presence of cuticle is a distinctly retarding factor, 
and in the absence of hydathodes or glandular hairs the surface absorption 
of a much cuticularized surface is practically nil. The presence of wax or 
bloom which makes the leaf practically unwettable is also a character 
which prevents any appreciable surface absorption, and those succulent 
plants which have bloom are not those which can absorb freely. The hairs 
1 Holtermann, Dr. C. : Der Einfluss des Klimas auf den Bau der Pflanzengewebe, 1907. 
2 Burgerstein, Dr. A. : Die Transpiration der Pflanzen, 1904. 
3 Burgerstein, Dr. A. : Ubersicht der Untersuchungen iiber die Wasseraufnahme der Pflanzen 
durch die Oberflache der Blatter, 1891. 
