Stimulation of Root Growth in Cuttings 95 



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to roots. The tables already presented show that this is not the case 

 with the permanganate treatment. In the experiment recorded in table 5 

 (page 89) there is practically no difference between top growth in the 

 treated twigs and in the checks, and yet there is a very great difference 

 in root development (fig. 5, page 90). The results obtained in the 

 warm-bath treatment (table 6), and in four cases in which the twigs 

 were treated with potassium permanganate after the rest period, showed 

 that both top and root growth were better in the treated twigs than in 

 the checks (fig. 5). This proves clearly that in these cases the roots 

 did not develop at the expense of the tops. It is to be noted here that 

 if the treatment is applied early in the rest period it generally has little 

 or no effect on top growth even for some time after the buds start; while 

 if it is applied after the rest period, tho the buds may start equally the 

 shoots of the treated twigs usually soon surpass those of the checks in 

 development, so that the length and the dry weight of both the tops and 

 the roots exceed those of the checks. With the stronger concentrations, 

 however, a point is apparently reached where there is still stimulation of 

 root growth but at the same time a distinct retardation of top growth. 

 This is well illustrated in table 10 (pages 106-7), which shows that the 

 stronger solutions of both potassium permanganate (KMn04) and ferric 

 chloride (FeCls) increased root growth but clearly decreased top growth. 

 Weaker solutions stimulated both tops and roots. Accompanying the 

 increased growth of tops and roots there is at first a lessened dry weight 

 of the stem. After continued growth, however, the stems become heavier, 

 probably due to the increased photosynthetic activity of the larger tops. 

 On the other hand, F^aivre (1871) has shown that in some cases the 

 tops may develop at the expense of the roots. He found that after the 

 buds had formed shoots there was insufficient food left in the stem for 

 root formation. The rooting process seems, as a rule, to be slower than 

 growth of tops, so that if the tops are in a condition to grow they will 

 develop faster than the roots and deplete the food supply, or else, as suffi- 

 cient water for the increased transpiration is not supphed, the shoots 

 will die, causing the twigs to wither at the same time. As stated earlier, 

 cuttings of various species were taken in late autumn before the end 

 of the rest period and were set out in the greenhouse benches. The tops 

 of most of these remained dormant until March or later, while the roots — 

 or the callus in the case of the twigs of Pyrus — proceeded to develop 



