96 Otis F. Cuetis 



vigorously. The buds on the twigs of the same forms taken in January 

 started to grow within two weeks after the cuttings were set out. In 

 the majority of such cases the young shoots, as well as the cutting itself, 

 soon withered and died from lack of water. With Ligustrum, however, 

 root development was so rapid that the majority of the twigs remained 

 ahve. Whether this is a matter of food distribution or merely a water 

 relation is not clearly shown by these experiments. 



Effect of treatment on respiratory activity 



The explanations of stimulation of root growth which have thus far 

 been discussed have been shown to be insufficient to fully account for 

 the increased growth resulting when cuttings are treated with potassium 

 permanganate. A more probable explanation appears to be that the 

 manganese increases the rate of respiration in the treated twigs or causes 

 more complete oxidation, thereby preventing the accumulation of inhibiting 

 or toxic products of catabolism. 



It has long been recognized that good aeration is essential for root 

 growth either of seedlings or of cuttings, and especially of the latter. 

 De Saussure (1804), early in the nineteenth century, pointed out the fact 

 that oxygen is necessary for root growth of seedlings. He grew chestnut 

 seedlings in flasks containing air, nitrogen, hydrogen, and carbon dioxide, 

 respectively. The carbon dioxide was distinctly injurious to the roots, 

 while the other gases did not allow for growth and the roots soon died. 

 It is commonly understood that one of the chief reasons for the practice 

 of soil drainage is to provide better aeration. Stoklasaand Ernest (1908) 

 have shown that poor aeration of root systems leads to the formation 

 of compounds such as acetic and formic acids within the roots, which 

 may result in their death. 



Harris (1914) and a number of other investigators have shown that 

 the growth of roots and the depth to which they penetrate are closely 

 correlated with the water content of the soil and the height of the water 

 table. Harris, as well as several other investigators, states that this is 

 probably due to the fact that a high water content excludes oxygen and 

 the lack of oxygen limits root development. 



There is apparently an even greater need for good aeration in soils in 

 which cuttings are placed, than exists for seedlings. This fact has been 



