102 
Journal of Agricultural Research 
Vol. XXIII, No. a 
beads which break up the current of air as it rises and take the place of 
the platinum disks of the Reiset tubes. 
Sachs (in Grafe, 6) drew the respired air through a series of simple 
absorption bottles, Kostytschew (13) used Giessler bulbs, and many 
other devices have been used by others. 
With sufficiently large quantities of actively respiring material, appa¬ 
ratuses of this type are excellent for determining one side of the respiratory 
reaction. They have the advantage of avoiding the disturbing effects 
of changes in the partial pressures of oxygen and C0 2 , but they neglect 
entirely the question of the amount of oxygen absorbed by the respiring 
material, which is quite as important as, and not always in proportion to, 
the amount of C 0 2 given off. 
Fdrthermore, they are not adapted for use with limited quantities of 
very small or relatively inactive seeds, as the amount of C0 2 given off 
in reasonable time may in this case fall within the limits of error of the 
method. Unless special precautions are observed, the experimental 
errors are likely to be rather large. 
(2) ABSORPTION BY CAUSTIC SOLUTION OP THIS C 0 2 RESPIRED IN A CLOSED 
SPACE WITH OR WITHOUT SIMULTANEOUS MANOMETRIC MEASUREMENT 
OF THE OXYGEN ABSORBED 
The apparatus used by Wolkoff and Mayer (32) was simply an in¬ 
verted U-tube, one arm of which dipped into a dish of mercury, while 
the other arm was much enlarged and received the plant material and a 
dish of caustic solution. This end of the tube was, of course, closed dur¬ 
ing the experimental period, and the whole apparatus was immersed in 
a water bath. 
Godlewski (5) cultured his material in a closed flask which contained 
a dish of caustic solution and was connected with a one-arm open ma¬ 
nometer dipping into mercury. Stich ( 24 ) modified this apparatus for 
effective temperature control by immersion in a water bath. 
When the manometer is used, this type of apparatus gives both 
oxygen consumption and C 0 2 production, but since the C 0 2 is absorbed 
as rapidly as it is given off and does not therefore compensate for the 
oxygen absorbed by the respiring material, the method often involves 
relatively large changes in pressure during an experimental period; 
these pressure changes might in some cases affect the results. Besides, 
like the preceding type of apparatus, this type requires special care to 
avoid errors due to the absorption of C 0 2 from sources other than the 
respiration of the material being studied and is not adapted for use with 
limited quantities of very small material. 
(3) INCUBATION IN A CLOSED SPACE, WHICH IS NOT SUPPLIED WITH 
Either caustic or manometer, with occasional SAMPLING of the 
AIR FOR ANALYSIS IN SOME FORM OF MICRO-APPARATUS, OF WHICH 
THE BONNIER-MANGIN APPARATUS IS PERHAPS THE BEST. THIS APPA¬ 
RATUS AND ITS USES ARE DESCRIBED IN DETAIL BY THODAY (26). IT 
HAS BEEN WIDELY USED DURING THE LAST 35 YEARS 
In the use of this method seeds have frequently been incubated for 
respiration in tubes inverted over mercury, but, as pointed out by one 
of us (p), the contact of the seeds with mercury may so alter their be¬ 
havior as to make the use of this method entirely out of the question in 
specific cases. 
