WM. CROCKER 
condition, but as we shall see later not all seeds lying dormant in the 
soil for thirty years or more are in this condition. Lepeschkin finds 
evidence for the presence of a re-dispersal process in fully imbibed 
plant cells. At ordinary temperatures he believes this increases many 
fold the life duration of plant cells. It and many other factors such 
as change in reaction of the cell may modify the speed of coagulation. 
Here too it is possible that carbon dioxide or other narcotics produce 
a state of rigor thereby greatly lengthening the life of the seed as 
is indicated by the work of Kidd. It is possible that seeds like 
Amaranthus retroflexus and Brassica nigra, lying in the soil for thirty 
years or more nearly or quite saturated with water, entirely consume 
their stored food in respiration and die of starvation. It is not known 
whether these seeds remain alive longer in this condition or in air-dry 
storage. 
The changes involved in the rapid loss of vitality by seeds that will 
not withstand drying are still more obscure. The nature of the injury 
produced by drying is also entirely unknown. 
Causes of Dormancy 
In securing delayed germination of seeds, plants are not limited 
to the dead monotony of one method. As one studies the problem 
more fully he wonders whether there is any conceivable method of 
securing delay not made use of in one plant or another. I believe 
that failure to grasp the variety of methods and the counter attempts 
to explain all delays by one or at most two methods, is the main 
source of the controversy, error and confusion that have prevailed in 
this field. 
We will now consider two general topics: (i) Methods of securing 
dormancy and (2) methods of overcoming it, or the action of forcing 
agents upon dormant seeds. The two topics are far from distinct. 
Certain subheads under either topic could be shifted to the other 
without violence, thus constituting an extremely complex interrelation 
between the general topics and the subheads under them. The classi- 
fication here offered is for the convenience of discussion and must be 
subject to change with growth of knowledge in the field. Nevertheless, 
I believe some such classification very desirable at this time in clearing 
up a chaotic situation and in giving future experimentation direction 
and aim. 
