46 s 
Influence of Carbon Dioxide . IV. 
With the intermediate concentrations of carbon dioxide, following 
which the injury occurring is much less, 1 the correlation between germina- 
tion and injury is not so great. Thus, following 50 per cent, carbon dioxide in 
the absence of oxygen, only 20 per cent, of the seeds showed visible injury 
to the radicle although all germinated and none showed secondary 
dormancy. Nevertheless, the conditions in the absence of oxygen are 
undoubtedly injurious, and do, if maintained, result in death. If the 
internal reactions which cause injury in the embryo are also those which 
are responsible for germination, as the correlation observed in the above 
experiments indicates, this particular case is of interest in that it shows 
that these internal changes initiate growth in their early stages before they 
have proceeded far enough to produce visible injury and cell-death. 
Summing up the results of these experiments dealing with the con- 
ditions necessary for the production of secondary dormancy in Brassica 
1 This in itself is remarkable, and is to be attributed to an effect of carbon dioxide in depressing 
anaerobic processes which give rise to toxic products (cf. Kidd, 4). 
