MECHANICS OF DORMANCY IN SEEDS* 
Wm. Crocker 
Introduction 
Dormancy in plants is common in three organs, seeds, spores, 
and buds. In this paper I shall limit myself entirely to the discussion 
of dormancy in seeds for three reasons : far more critical and analytical 
work has been done on dormancy in seeds than upon the other two 
organs; obscure correlation effects do not play as prominent a part 
as in buds; and I am best acquainted with this phase of the subject. 
The title of this paper might imply that I am aligning myself with 
the mechanists as against the vitalists; such is not the case. The 
vitalists can justly claim that in growth we have as yet explained so 
little by known chemical and physical laws and have so much etill 
to explain on this basis or on the basis of newly discovered laws that 
the title "Mechanism of Growth" would imply a very meager dis- 
cussion of our knowledge of this process. To date we have to discuss 
growth mainly in physiological rather than mechanistic terms. The 
situation is rather different with the dormancy of seeds. Here so far 
as the work is analytical, it indicates that dormancy is brought 
about by factors inhibitory to general processes preceding or accom- 
panying growth. 
In plants of the temperate zone, the seeds generally have a rest 
period. Howard^ finds that more than 75 percent of the species, 
wild and cultivated, growing around Columbia, Missouri, have a 
distinct period of dormancy. The rest period is more general and 
much more persistent among wild than cultivated forms. Selection 
resulting from methods of cultivation have largely disposed of this 
character in domesticated forms, as is well illustrated by the two 
closely related species, Avena fatua and A. sativa^ The former is 
delayed in its germination until the spring following ripening, con- 
* Invitation paper read before the Botanical Society of America and affiliated 
societies at Columbus, December 29, 19 15. 
1 Howard, Mo. Agr. Exp. Sta. Res. Bull. 17. 
2 Criddle, Dept. Agr. Ottawa, Bull. S-7. 
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