364 BOTANICAL GAZETTE [MAY 
are bad for the conducting of the experiments, and the more they are ~ 
kept out the more water is absorbed by the plant when attached to a 
pinometer. It is obvious that the plant must also guard against the 
accumulation of air in the column of water which fills the vascular 
system. No doubt this will in part account for the peculiar structure | 
of the woodelements. Do the latter bear any relation in their struct- 
ure to the nature of the water generally found in the localities in 
which the plant grows ? 
The form of pinometer mentioned in this paper is intended, as 
already mentioned, essentially for demonstration purposes. It is 
possible by its use to observe, more clearly than hitherto, the relation 
between shoot suction and root pressure. Owing to the preliminary 
nature of this paper I have refrained from giving any lengthy readings 
taken during the experiments. Their value in any case would not 
be very great, being taken with the simple form of pinometer here 
described. A more elaborate bit of apparatus is therefore in course 
of construction, by which any air making its appearance in any 
part of the pinometer is removed automatically at regular intervals 
without altering the conditions of pressure inside the system of tubes. 
Furthermore, it is connected with an automatic recording instrument, 
in which the difference in the height of the two mercury columns will 
be reduced as much as possible. 
The nature of this paper, I hope, will excuse my having made no 
reference to any literature. It was not my intention to discuss the 
old or bring forward a new theory with regard to the rise of water. 
We still have the suction by the leaves, the pressure by the root, and 
the as yet little understood lifting of the water by the wood. In 
writing this paper, it was my object to give an account of a very 
simple bit of apparatus. by means of which various phenomena con- 
nected with the transpiration stream in small plants could be readily 
observed. I hope later on to be able to publish some more detailed 
observations on the properties of the wood lift, taken by more 
elaborate instruments. 
Diagrams illustrating the working of the pinometer were shown 
at the last Cambridge meeting of the British Association. 
UNIVERSITY OF MANCHESTER, ENGLAND. 
Spas at's Te Se aa a ee er ee 
eT at ee ee ee ee 
