﻿BOTANICAL GAZETTE 



Untreated tubers were planted in the sawdust just outside of 

 the moist chambers. The sawdust was kept constantly wet 

 (table XXI). 



TABLE XXI 



3 per cent dioxygen 28 days 



Table XXI is typical of a number of experiments that were per- 

 formed with new potatoes. Such treatment failed, however, to 

 shorten the rest period of tubers with heavily suberized skins; this 

 alteration of the skin doubtless renders it impermeable to hydrogen 

 peroxide. Numerous attempts to control these experiments by 

 wrapping tubers in cotton saturated with distilled water usually 

 failed on account of the decay of the tubers. It may be assumed, 

 however, that the partial oxygen pressure in the wet sawdust would 

 not be less than that under saturated cotton. 



Respiration.— It has been shown that the rest period of potato 

 tubers can be either entirely eliminated or greatly shortened by 

 means which would seem to facilitate the oxygenation of the internal 

 tissues. That a great increase in oxygen absorption actually occurs 

 is proved conclusively by the effect of the various treatments on 

 respiration, the rate of which was determined by the amount of 

 carbon dioxide expired from the tubers. Ten tubers, with a total 

 weight of about 1500 gm., were used for each determination, which 

 was allowed to run 24 hours at room temperature. The control 

 determinations were made at the same time and under exactly the 

 same conditions. 



The amount of carbon dioxide expired from new potatoes with 

 thin, slightly suberized skins is much greater than that from the 

 same tubers after the skins have become well corked and adherent 

 to the underlying tissues. When the latter character of the skin 

 is attained, the rate of respiration under uniform conditions remains 

 fairly constant until the beginning of sprouting. Table XXII is 

 a typical experiment which will suffice to show this fact. Immature 



