60 BOTANICAL GAZETTE [JULY 
coincide by this method of recording, six experiments of two to 
five days’ duration have been performed. The graphs shown in 
fig. 5 exhibit the actual ratios for 2-hour intervals in comparison 
with the average ratio for the entire experiment, for synchronous 
records of two vaporimeters (A), two irrigated pelargoniums (B), 
and two pelargoniums watered at 24-hour intervals (C). These 
partial records are sufficient to show that variations in the ratios 
between records must be greater than o.3 in order to be significant. 
It will be readily seen that the variations in the actual records 
sufficient to produce this variation in the ratios are very small 
fractions of a gram in most instances. There are various explana- 
tions for these minor irregularities: the impossibility of estimating 
the hourly loss accurately when the gram-interval extends over 
several hours; shadows made by the framework of the green- 
house; differences in exposure to light; differences in irritability, 
etc. Whatever their causes, they must not be overlooked in com- 
paring plants of different species and different habitats. 
EASTERN ILLinors STATE NORMAL SCHOOL 
CHARLESTON, ILL. 
