88 Otis F. Curtis 



reasons of stimulation 

 Possible effect on food supply 



In seeking the cause of the stimulating effect of potassium permanganate 

 on root growth, it was thought possible that the treatment changed the 

 food stored in the stem of the cutting so as to make it available for 

 immediate use. In order to determine whether this was the case, cuttings 

 were treated as in the preceding experiments for twenty-four hours and 

 then placed in flasks of distilled water. Microchemical tests for sugar 

 and starch were made at intervals of two days at first and of from seven 

 to ten days later. In no case was there any loss of starch or production 

 of sugar to be detected until rapid development of callus and roots started. 

 When the callus was well formed, the starch in the immediate proximity 

 of this tissue was disappearing, but no change was visible in the starch 

 content at a distance of from three to four millimeters from the callus. 

 In spite of the fact that the food remained unchanged until growth started, 

 the treated twigs showed marked stimulation. When the roots were 

 measured, those on the treated twigs averaged 5.32 times those of the 

 checks — an increase of 4S2 per cent. It should be pointed out that 

 the method of testing is not deUcate enough to permit detection of sUght 

 changes in sugar or starch content. 



It has occurred to the writer that the precipitation of manganese dioxide 

 in the base of the stem may so clog the tissues as to check the loss of 

 organic matter from the cut end. As a result of this check, more food 

 might be available for root formation. This explanation has not been 

 verified experimentally, but it would seem that it is of minor importance. 



Relation to rest period 



In many cases cuttings were taken in autumn, when they were still 

 in the resting condition. It seemed possible, therefore, that the treatment 

 might have served to bring either the entire twig or its basal part out of 

 the rest period. If such were the case, the increased root growth might be 

 merely due to the fact that the growth had started earlier in these twigs 

 than in the checks, in which case there would be no true root stimulation. 



Effect on rest period of twig as a whole. — In order to ascertain the 

 effect of potassium permanganate on the rest period of the twig as a 

 whole, Ligustrum cuttings were made on October 15, 1915, and were 

 given continuous treatment as indicated in table 5. As shown by the 



