Stimulation of Root Growth in Cuttings 77 



In choosing a form with which to experiment, there were several 

 points that had to be considered, as follows: 



1. Large numbers of cuttings must be available. 



2. The cuttings must be uniform with respect to size, shape, age, 

 position on parent form from which they were taken, and conditions 

 under which they were grown. Otherwise they would be likely to root 

 unevenly. 



3. Uniformity in rooting was a very important factor, for without 

 uniformity there was found to be a large probable error which would 

 necessitate the using of great numbers of twigs for each treatment, thereby 

 complicating and increasing the mechanical labor involved. In view 

 of the fact that in these experiments over twelve thousand cuttings of 

 Ligustrum were actually used in addition to four thousand cuttings 

 of other species, it is obvious that the problem would be rendered more 

 difficult if it were necessary to increase the number of cuttings as much 

 as five to ten times. 



4. It was important that cuttings should be used which would root 

 in as short a time as possible. The field of research is new, and if one 

 were forced to wait two months or more for results on preliminary tests 

 the experiments would be long drawn out or it would be too late to 

 obtain cuttings for a second set. The writer experienced this trouble 

 for three consecutive years, even with comparatively quick-rooting 

 Ligustrum. On those occasions the December freezes had killed the 

 twigs on the bushes at about the time when the first set of cuttings 

 was showing results. Furthermore, the immature condition of the twigs 

 rendered impossible an earlier beginning of the preliminary experiments. 

 The use of hardy forms would not solve this difficulty, for, tho freezing 

 would not kill the twigs, it would bring them out of the resting condition, 

 which would be detrimental to rooting. 



5. It was necessary to choose a form that would root readily. Com- 

 parative results could thus be obtained which would allow for 

 manipulation to determine more nearly the optimum, treatment. 



Ligustrum ovalifolium Hassk. most nearly fitted the requirements 

 outlined, and therefore it was used in the majority of the experiments. 

 The following forms also were used: Cydonia oblonga Mill., Ribes 

 Houghtonianum Jancz., Pyrus malus Linn., Prunus cerasifera Ehrh., 

 Kerria japonica DC, Evonymus europaea Linn., Berberis Thunbergii DC, 



