EFFECTS OF REST AND NO-REST PERIODS UPON 
GROWTH OF SOLANUM 
W. F. GERICKE 
That important chemical and physiological changes occur in 
plants, seeds, and bulbs during their rest period has been shown 
by several investigations. These investigations have been carried 
out with a considerable number of plants, seeds, and bulbs. Those 
studies which concerned themselves with the changes in the compo- 
sition of the potato have been found of especial interest to the 
present study because of the light they have thrown upon the 
importance of the chemical changes in the composition of the tubers 
on the later physiological activities of the plant. 
Briefly touching on some of the literature of rest period studies _ 
in which the chemical aspect of the problem was considered, we 
find that the subject matter resolves itself into three general 
phases: (a) the influence on the permeability of the integument, 
(b) the influence on the chemical changes in the embryo, (c) the 
influence on the reserve food material. 
CrockER (2) has explained some of the causes of delayed 
germination as being due to the resistance of the integument of 
the seed to water and oxygen. His experiments with X anthium 
showed very clearly that the long dormant period of one of the 
embryos was simply a question of the imperviousness of the seed 
coat. Thus in this case the problem of the so-called rest period 
resolved itself into the adoption of a method to overcome the resist- 
ance of the seed coat and to allow water and oxygen to penetrate 
the tissues. 
ECKERSON (3) found that after-ripening processes also involved 
_ chemical changes in the embryo. The water-holding capacity 
and the reaction of the embryonic tissue of Crataegus, the species 
used for the experiment, were found to change during the rest 
period. Cotyledons and hypocotyls gave different kinds of 
reactions during the after-ripening processes, due to the results © 
of enzymatic activities. 
Botanical Gazette, vol. 65] [344 
