- 1906] CROCKER—DELAVED GERMINATION 275 
lary tube sealed at the upper end with wax; c’, a small graduated 
tube by which the rate of diffusion of oxygen is to be ascertained; and 
a,anair chamber, After s is furnished with 300°° potassium pyro- 
gallate the whole apparatus, excepting pinchcock 1 and the portions 
of tubes c and c’, is immersed in a water bath regulated to the desired 
temperature within .or°, After the apparatus has had sufficient 
time to attain the temperature of the bath, pinchcocks 1 and 2 are 
loosened; the plugged end of c filed off; and the pryogallate forced 
into f. Now c is resealed 
and the pinchcocks reclamped; ee 
a drop of water is allowed to 1 
enter the graduated tube c’; . 
and the rate of diffusion of 
the oxygen is read by the rate 
of the movement of the drop 
in tube c’. The same seed : 
Coat can be used repeatedly 
at temperatures to be com- 
pared. Numerous measure- 
ments made in this way 
Showed the rate of diffusion 
1.4 t0 1.6 as fast at 33° as 
at 19°,? 
The amount of CO; 
evolved is considered the best 
measure for the amount of 
respiration occurring. It is 
evident from the measurements 
recorded above, that if the ratio CO,:O, remains constant with the 
"ise In the available oxygen due to the rise in temperature, the amount 
of carbon dioxide evolved will increase from 1 to 1.4-1.6 as the 
temperature rises from 19° to 33° with the seed coats intact. If it 
happens, however, that the ratio CO,:O, rises in value along with 
the rise in the rate of the diffusion of oxygen, then the increase in 
respiration with this rise in temperature will be still more marked. 
Vics 
Ma tat 
Hhiy, 
— 
ries 
Q 
ii 
TELA 
Hliiyl 
(RUBS 
t 
Fic. 3.—Apparatus for testing permeability 
of seed coats of cocklebur to oxygen. For 
description see text. 
: When the coat was allowed to dry somewhat the rate of diffusion was also 
Sreatly increased. 
