Visual differences in root growth at this stage of the experiment are quite striking.  The front plant of Tank 2 shown in Figure 1, for example, has no secondary roots and but one primary root.  The plant from Tank 4 shown in Figure 2 likewise has only one primary root, but it is clearly longer and thicker than that of the plant from Tank 2;  and it has several secondary roots emanating from it.  The plant from Tank 6 in Figure 3 is similar in this regard; but its new-vine shoot has grown so long that there are two new primary roots coming from it.  These differences for all front plants of all six tanks are again expressed graphically in Figures 4-6.