29 



The experiment shown in llie preceding table represents the results- 

 obtained by cutting primary roots on the growtli of the stems (liypo- 

 cotyls) of the sunflower. All but three centimeters of the primary 

 roots were removed and the differences in the daily increase, in the 

 normal and cut plants, are represented by the percentages at the 

 bottom of the table. It will be noticed that the growth of the cut 

 plants was less that of the normal ones throughout the experiment 

 which lasted seven days; also that the decrease, or retardation, in 

 the growth of the cut plant as compared with that of the normal was 

 greatest at first, and that the cut plants made considerable attempt 

 towards recovery. The actual relative position of the normal and 

 cut plant as regards growth after cutting is shown by the percentage 

 of total growth. A correlative effect usually manitests itself in experi- 

 ments of this nature in the formation of numerous secondary roots 

 near the cut surfaces of the primary roots. 



The following experiment shows the effect of splitting the pri- 

 mary roots upon their growth. 



Table XI, Kxperiinent showing the effects of splitting on the growth 

 of primary roots of Vicia Faba. 6 plants used, 3 normal 

 and 3 cut. Primar) roots split between points 20 and 30 

 millimeters from their apexes. Plants cultivated in saw- 

 dust. Growth of normal plant equals loo'/f. 



.\vera8e daily growth in millimeters. 

 12 34567 



Normal 12.3 24.6 19.3 26.0 15.3 15.0 13.3 



Split 7.0 17.6 32. o 22.6 18.6 44.0 17.3 



Percentage ) Daily growth 56''/ 71''/ 113'/ 87''/ 121'/^ 93*/^ i3o'7f 

 Split to unsplit \ Total growth 96''/ 



Original length of roots 3 centimeters. 



Unlike the preceding experiment where the cutting was more or less 

 removed from the measured growing zones, we have here the region 

 of mutilation coinciding closely with the zones of measured growth. 

 At first a similar retardation as the result of mutilation or splitting 

 the roots is shown here as in the preceding experiment. Later a con- 

 siderably accelerated growth of the mutilated plants took place. At 

 the end of seven days the plants with split roots had nearly reached 

 the same length as the normal plants. 



