496 
Delf. — Transpiration and Behaviour of 
HI. Absorption of Water by Green Parts in 
Halophytes. 
In Fig. 9 the relative 1 rates of transpiration during withering are 
shown graphically. It will be seen that, apart from effects of variations in 
the physical environment, the two succulent types, Salicornia and Sedum , 
show a water loss not only greater but more constant than that of the Vicia 
leaf. Probably the stomata in each case were closed, at any rate after the 
first half-hour, but in the first two plants, on account of the lack of cuticle 
and perhaps also the presence of aqueous tissue, this is an insufficient check 
to the transpiration in the dry air of the laboratory, although the wilting 
which ensues is less obvious than in the case of a mesophyte. 
Notwithstanding the comparatively rapid transpiration any species of 
Sedtim can be grown successfully in a dry atmosphere if a supply of water is 
given to the roots ; but in my experience this is not true of Salicornia and 
some other halophytes ; on the contrary, this plant appears unable to absorb 
enough water by its roots to make good the loss due to transpiration in the 
dry air of a laboratory 
On July 19, 1909, a test experiment was performed to determine the 
transpiration and absorption of a young, healthy, and uninjured Salicornia 
plant in the comparatively dry air of the Cambridge Botanical Laboratory. 
The plant, which appeared to be perfectly turgid, was washed carefully free 
from soil, dried, weighed on an accurate balance, and placed with the root 
dipping into a known amount of water in a weighed vessel. A control 
vessel of water stood near, and was used to give the evaporation from the 
exposed water surface in the experimental vessel. After an interval of two 
hours, the plant was removed, dried, and weighed, and the vessels of water 
also weighed. On estimating the transpiration and absorption it was found 
that the plant had transpired 16 %, but had absorbed only 14 % of its own 
fresh weight, thus showing a loss of 2 % of its own fresh weight. 
Such a deficit in the water supply obtained from the roots is, probably, 
common in nature, in spite of the moist habitat ; and it is compensated, at 
least to some extent, by the power which this plant undoubtedly possesses of 
absorbing water freely over its whole surface, 2 which is capable of being 
easily wetted. It seemed worth while to make- some observations on the 
absorptive power in this and other plants. 
Three young plants of Salicornia annua were cut just above the level of 
the highest internode which was at all faded, and the cut ends were sealed 
with wax. The plants were then dipped into water, dried thoroughly with 
blotting-paper and a soft cloth, and weighed separately. They were then 
1 Livingston (’06) : The Relation of Desert Plants to Soil, Moisture, and Evaporation. 
2 Cp. Pfeffer, W. (’00) : The Physiology of Plants, English Edition, vol. i, p. 160. 
