Stimulation of Root Growth in Cuttings 91 



may have started growth in the basal part, leaving the tops dormant, 

 for in some instances the roots of the treated twigs started from three 

 to ten days earlier than those of the checks. This difference in time 

 of starting, however, is insufficient to account for the great difference in 

 growth. 



As shown by table 5, the roots of the treated twigs when they had 

 been visible less than two weeks (on November 29) showed growth more 

 than three times that in the checks when the roots of the latter had been 

 visible for at least three weeks (on December 18). Furthermore, as a 

 result of the exposure on November 29, when the cultures were being 

 photographed, the roots in the permanganate cultures Were partly broken 

 and dried, so that when measured the second time many of the roots first 

 formed were completely rotted or the ends had died back and new branches 

 were starting. The checks were not injured for no roots had started at 

 that time. In spite of this injury to the treated twigs, the growth was 

 much better in these than in the checks and continued better as long 

 as the cultures were kept. This great difference in root length at the 

 time of the final measurements, which were taken more than twelve 

 weeks after growth had commenced, cannot be explained on the ground 

 that the treated twigs had a start of ten days. 



Stimulation of root growth in twigs that have passed the rest period. — The 

 following experiment^ furnish additional proof that the stimulation of 

 root growth by potassium permanganate has nothing to do with the 

 rest period. Cuttings of Ligustrum were taken on December 8, 1915. 

 The bushes from which they were taken had been twice subjected to 

 several days of freezing weather, and, as is brought out later, these twigs 

 had passed out of the resting condition. One hundred and fifty twigs 

 were treated for twenty-four hours in water, and the same number in 

 0.1 molecular potassium permanganate. After being rinsed, duplicate lots 

 of ten twigs from each treatment were placed in distilled water in a cool 

 room at a temperature of from 5° to 10° C, thirty twigs of each treatment 

 were placed in sand in a somewhat warmer, shaded greenhouse at from 

 10° to 15° C, arid one hundred twigs of each treatment were placed in 

 sand in a still warmer, unshaded greenhouse at from 18° to 22° C. 



The buds of the twigs in the warmest house started almost immediately 

 after the cuttings were set out. They were not in the resting condition, 

 and the treated and the untreated twigs started equally; but by the 



