1918] GERICKE—SOLANUM 345 
As early as 1890 JOHANNSEN (5) studied the effects on after- 
ripening of ether treatment. His work with the chemical changes 
in the after-ripening of bulbs led him to conclude that the lack of 
growth or the slow growth of the plant during the so-called rest 
period was not due to the lack of soluble food. His ether treatment 
of bulbs decreased the length of the exbpitels pens ea iod, - was 
1 
unable to Cpl tany impor t ant 
save that amide nitrogen seemed to have been increased in amount, 
MULLER-THURGAU and SCHNEIDER-ORELLI (7) conducted an 
extensive investigation on the chemical and enzymatic changes in 
potatoes during the storage period. They found that the intensity 
of respiration was increased by a certain rise in temperature. 
Respiration likewise was increased with the relative age of the 
tubers. The increased respiration varied with the sugar content, 
and active enzymes were present at all stages of the rest period. 
A certain equilibrium between starch and sugar formation was 
observed. 
APPLEMAN (1) found diastatic activity greater in cold storage 
potatoes than in those stored at room temperature. After-ripening 
was found to affect the buds rather than the tubers. The chemical 
changes of after-ripening concerned carbohydrates chiefly. Pro- 
teins, lipoids, organic extractives, and inorganic phosphorus 
remained constant up to the time of sprouting, and no changes were 
discernible in the proteolysis of the various nitrogen compounds. 
Metabolic changes of the proteins began rather suddenly, and were 
found to be concurrent with sprouting, but were not considered the 
primary processes of after-ripening. 
Howarp’s (4) work on factors concerned with the rest period 
. is of great interest, both as to the extent of his investigations and as 
to the bibliography of the subject. His experiments show, as 
Ktess (6) had already indicated, that the rest period is not a fixed 
or unchangeable character of plants, but is instead a condition 
brought about by internal and external agencies. Both Howarp 
and Kiess concluded that although the morphology of a plant is 
linked up within the protoplasm and the specific structure of the 
cells, external conditions are of great importance in determining 
certain outward forms of plant responses. 
