2a ne ee = 
t8 2-20 
A NEW SELF-REGISTERING TRANSPIRATION 
MACHINE. 
EDWIN BINGHAM COPELAND. 
TRANSPIRATION is so important and conspicuous a function of 
ordinary land plants that the number of papers dealing with it, 
as a whole or in part, sufficed already a decade ago to justify the 
compilation of ‘the materials for a monograph.”” No contribu- 
tor to this literature can have failed to feel the need of some 
device by which he could record the plant’s loss of water, with 
such ease and accuracy as various auxanometers, for instance, 
make possible for its growth. Several contrivances for this work 
have been described, and a few have been put to actual use by 
their inventors; but none has as yet been well enough adapted 
to the purpose to bring it into general use, or make it any stand- 
ard part of laboratory equipment. 
Pfeffer* refers for such apparatus to papers by Vesque, Eder, 
Krutizky, Marey, and Anderson. Eder? measured only the 
absorption of water. A tracer fastened to a cork floating ina 
burette from which the water is drawn makes the absorption self- 
registering. The apparatus used for investigation by Vesque 
was not self-registering, but was simply a glass siphon with the 
shoot being tested in one end, and filled to a given point in the 
other arm with water, and weighed ; after a time it was reweighed, 
showing the weight of water transpired, and filled to the original 
level and weighed, showing the weight absorbed. Absorption 
and transpiration are not necessarily equivalent, for any given 
time-interval. Krutizky’s* apparatus consisted of a siphon into 
* Pflanzenphysiologie ¥.5 224. 1897: [id 2.) 
* Untersuchungen iiber die Ausscheidung von Wasserdampf bei den Pflanzen 106. 
Leipzig. 18 
3 L’absorption comparée directement a la transpiration. Ann. Sci. Nat. Bot., VI. 
‘Beschreibung eines zur Bestimmung der von den Pflanzen aufgenommenen und 
verdunsteten Wassermenge dienenden Apparates. Bot. Zeit. 36 : 161. 
ne 343 
