﻿2Q2 BOTANICAL GAZETTE [april 



growing conditions, which include in this case the maximum partial 

 oxygen pressure of the atmosphere. The elimination of the rest 

 period by this means is not due to water absorption from the 

 exterior, as tubers with skins removed will sprout, even in dry 

 storage, much earlier than those with skins intact. 



If tubers are cut in half transversely or cut into half-inch slices, 

 the buds on the stem half located near the exposed surface will 

 sprout much earlier than normally, provided suberization of the 

 surface cells is prevented. This may be accomplished by laying 

 them on wet soil, or, better still, sawdust, and covering with wet 

 excelsior. Sprouting in this case also was not due to water absorp- 

 tion, because the rest period of these buds may be greatly shortened 

 in dry storage if drying of the exposed surface is prevented by 

 covering it with a thin layer of paraffin. 



The earliest sprouting occurred when the skins were removed 

 and the tubers also cut in the manner described above. 



Subdued light stimulates growth in buds on new tubers with 

 slightly suberized skins. The evidence at hand makes it highly 

 probable that this effect is due to greater oxygenation of the tissues 

 by photosynthesis. The light influence entirely disappears when 

 the skin is removed. Subdued light does not stimulate growth in 

 the buds on tubers with highly suberized skins; the effect is rather 

 one of retardation. 



The rest period of new potatoes may be shortened by wrapping 

 the tubers in cotton saturated with hydrogen peroxide. The 

 abundance of catalase in potato tuber decomposes the hydrogen 

 peroxide diffusing through the thin skin, liberating free oxygen. 

 This treatment had no effect on old tubers on account of the imper- 

 meability of the heavily suberized skin to the hydrogen peroxide. 



All the foregoing treatments greatly accelerate the rate of respi- 

 ration. It may be safely concluded, therefore, that the elimination 

 or abbreviation of the rest period under the conditions employed in 

 this work is correlated with increased oxygen absorption. 



The rest period of the potato tubers is not firmly fixed and 

 hereditary. It is not of internal origin due to autogenic metabolic 

 changes, as it can be entirely eliminated by means which maintain 

 a proper adjustment between the bud tissues and external agents, 



