180 BOTANICAL GAZETTE [SEPTEMBER 
mined, by weighing and measurement, the weight of 1°¢™ of paper, 
The results are tabulated below: 
Area, Sq cm Weight. gr. Avene =e 
peer A wees sh. 229.852 3.642 0.01584 
DME Dac ecas ss 109.650 1.772 0.01616 
ert neers. 70.992 1.098 0.01547 
BHaeet Deien oc cs 49.210 O77 0.01565 
__ Average weight of 1°1™, by all tests, 0.01573; greatest variation from 
average, 0.00043; greatest variation from average in per cent. of average, 2-7 P# 
cent. 
3 Fic. 1 
From these figures and other similar ones it appears that a 
paper so treated is uniform within 3 per cent. of error. Sin 
Its as that 
the planimeter method gives approximately the same resu 
by weighing, the two methods can be used interchangeably. 
former is the more direct and consumes less time and energy» *° that 
where the instrument is at hand it should be used for this sort of work 
In both soil and water cultures a number of duplicates Wet’ . 
carried through so far as transpiration was concerned. In SY 
cases, owing to the great amount of work involved, the other uses 
Hrements were made for only one series and not for the duplicat 
The experiments, results of which are recorded in the presen 
