134 AMERICAN JOURNAL OF BOTANY [Vol. 9. 
Table 22. Measurements in Cross Section of Meristematic Root Cells of Cuttings of Trees of 
Salix 7iigra, Group A 
Ave. Measure, 
Number of Tree Diameter of Tree s Cells 
(Inches) (Microns) 
364 —I 10.29 X 10.29 
733 I 9.29x11.28 
Average 9.79x10.78 
Table 23. Measurements in Cross Section of Meristematic Root Cells of Cuttings of Trees of 
Salix nigra, Group B 
Ave. Measure, 
Number of Tree Diameter of Tree 5 Cells 
(Inches) (Microns) 
58 4 II. 74x11.39 
62 4 10.95x13.28 
68 4 7-30 x 9.62 
617 4 8.96x10.45 
641 6 12.28 x 12.61 
Average 10.24x1 1.47 
Table 24. Measurements in Cross Section of Meristematic Root Cells of Cuttings of Trees of 
Salix nigra, Group C 
Ave. Measure, 
Number of Tree Diameter of Tree 5 Cells 
(Inches) (Microns) 
35 10+ 10.95 X 11.62 
44 10 8.63 X 9.62 
46 18 12. II X 11.28 
404 15 9-63 X 9.63 
602 20 7.97 X 10.95 
605 8 8.63 X 1 1. 61 
620 8 9.96 X 9.29 
628 8 11.95 X 11.82 
631 8-10 8.30x15.44 
643 10 10.79 X 14.94 
Average 9.89 x 11.62 
The measurements of the five cells of each tissue were averaged for 
each root measured. The averages thus obtained were averaged again 
according to tissues, and a grand average of cell measurements for each 
tissue was obtained. For example, the measurements of the five epidermal 
cells were averaged for each root. These averages were then added and 
averaged for the number of roots examined, so that the resulting grand 
average represented the average measurement for all the epidermal cells. 
A grand average was obtained for epidermal root cells from cuttings of 
Groups A, B, and C. These averages were then compared and tabulated 
as shown in tables 25 and 26. This procedure was followed for each root 
tissue present. 
From an examination of table 25 it will be seen that the average measure- 
ments of cross sections of root cells of cuttings from trees of Salix nigra 
