486 
Delf . — Transpiration and Behaviour of 
In 1894 Stahl published an account of his cobalt paper method, and he 
found by means of this test that in many halophytes there was a consider- 
able and sustained rate of transpiration. He asserted that in these plants 
the stomata appear to have lost the power to close, as is often the case in 
freshwater marsh plants. According to Stahl, the succulent habit has 
been developed as a compensation to reduce the transpiration, which can no 
longer be regulated by the stomata. 
In 1897 Rosenberg repeated a number of Stahl's experiments, but 
worked in the field, testing each leaf immediately after detaching it from 
the plant. By this means he found that whereas immediately after being 
detached the leaf produced a pink coloration in from one to three minutes, 
thus showing a rapid rate of transpiration, yet five or ten minutes after 
being detached the same leaf gave little or no coloration when in contact 
with the cobalt paper for ten or even twenty minutes. Some of the plants 
were uprooted and brought to a laboratory, and on testing, gave the slower 
rate of transpiration ; microscopic examination showed that in nearly every 
case the stomata were closed. Rosenberg suggests that this may have 
been due either to want of water, or to the darkness to which they were 
exposed while in the collecting-tin ; but in either case his results clearly 
show that, contrary to the opinion of Stahl, the stomata in halophytes have 
some power of movement, whilst the results of both Stahl and Rosenberg 
are in opposition to the commonly accepted view of Schimper, that halo- 
phytes are essentially xerophilous in habit. 
The present paper is the outcome of some experiments performed at 
Erquy in September, 1906, at the suggestion of Professor Oliver. Most of 
the work has been done in the laboratory at Westfield College, but in July, 
1909, owing to the kindness of Professor Seward, some observations were 
made at the Cambridge Botanic Laboratory. My thanks are due to Pro- 
fessor Oliver for supplies of fresh material of Salicornia annua , and for 
advice and continued interest throughout. 
In the following pages some account is given of measurements of the 
rate of water loss in certain typical halophytes, and of the power which 
these plants possess to absorb water by means of their green surface. Some 
observations on the stomata of Salicornia annua and Aster tripolium are 
also recorded, and these in the main support Rosenberg’s conclusion that 
the guard cells possess the power of movement. 
II. Measurements of Loss of Water due to Transpiration. 
(a) Method of determining transpiring areas. The method most com- 
monly employed in the determination of surface areas was that of tracing 
the outline on squared paper, and thus estimating the total surface exposed. 
When mesophytic leaves were used the tracing was done before detaching 
the leaf, or, where this was not possible, immediately after its removal from 
