56 BOTANICAL GAZETTE [yoy 
The extract was then filtered through four thicknesses of cheese- 
cloth, and finally through S. & S. filter paper no. 588. 
As previously stated, all tests were conducted with BUNZEL’s 
simplified oxidase apparatus. In this there is no provision made 
for absorption of the carbon dioxide produced, hence only compara- 
tive results can be obtained. It is probable, too, as BUNZEL points 
out (2, p. 30), that with no separate alkali solution in the apparatus 
a longer time is required for the reaction to come to an end, because 
of the slower absorption of the carbon dioxide by the mixture in the 
apparatus. This may partly account for the time required in the 
experiments described later, but it seems unlikely that a mercury 
rise which continued for 21 days in the absence of a means for 
absorbing carbon dioxide would have ceased within a few hours 
with such a means present. So far as BuNZzEL’s (2) published 
data are concerned, there is no evidence that oxidation would not 
have continued longer if his experiments had covered a longer 
period. REED (3) and AppLEMAN (4), using BUNZEL’s larger 
apparatus, though they do not state whether or not they used 
the alkali basket, set the limit for completion of the reaction at 
2-4 days. 
Corrections for temperature variations were made by running 
with each experiment a blank apparatus containing only water, and 
subtracting. from the readings in the others the reading above 
zero (negative pressure) in the blank. No readings were taken 
when the mercury in the blank stood below zero (positive pressure). 
It was feared that discrepancies might be introduced by the 
temperature variations, but as a matter of fact the differences 
between the results in any two comparable experiments were 
found to be no larger than those between duplicate apparatus in 
the same experiment. 
As a preliminary experiment (no. 1) an extract was prepared, as 
already described, from dried ground bark (sample 17) of a healthy 
Ben Davis limb 3 inches in diameter, and the apparatus set up as 
follows: 8, 9, 10, 11, 12, with 1 cc. ext.+1 cc. H,O+4 cc. 1 per 
cent pyrogallol; 13, with 6 cc. of distilled water. 
The shaking was performed by tipping back and forth six or 
eight times the wire culture-tube holder in which the oxidase appara- 
