2 BOTANICAL GAZETTE (yuLy 
While the respiration of most plant parts has been studied 
more or less, there are comparatively few data on resting seeds. 
For this reason the study of the respiration of seeds would be of 
interest, per se, and if dormant seeds were selected, it might be 
possible both to discover differences in the respiration of related 
and of unrelated species, and, through the acquisition of informa- 
tion upon the rapidity with which food reserves were utilized, to 
arrive at some idea of the probable longevity of the seeds. 
Most dormant seeds belong to one or another of certain main 
classes (CROCKER 14): those in which the dormancy is due to 
coat characters, as impermeability to water or to oxygen, acting 
in conjunction with some physiological character in the embryo 
aside from actual dormancy; or those in which dormancy is con- 
ditioned by the embryo itself, either through lack of differentia- 
tion or through the absence of some factor essential for germination, 
even when the naked embryo is exposed to all ordinary external 
germination conditions. In addition there are certain seeds with 
mature embryos whose coats apparently exclude neither water nor 
oxygen, but still germination is hindered; such delay in Alisma Plan- 
tago (15) is due to the inability of the embryo to overcome the 
mechanical resistance to expansion offered by the coats. Finally, 
dormancy may result from the joint action of two or more of these 
factors. 
In the investigation, some of the results of which are embodied 
in this paper, the original intention was to study the respiration of 
each type of dormant seeds, but during the progress of the work 
the comparative respiration of dormant seeds has become of prime 
interest, and this phase forms the subject of the present report. 
The seeds selected were three on which physiological studies 
had already been made, but for which respiratory data were lack- 
ing, namely, Amaranthus retroflecus, Chenopodium album, and 
Crataegus,* and in addition (because of their economic importance 
and the ease with which they could be obtained, as well as because 
of their relationship to Crataegus) seeds of the common drupaceous 
Rosaceae. In Crataegus and Amaranthus some attempt has been 
made to determine variations in respiration accompanying after- 
* The species chiefly studied was C. coccinea. 
