March, 1922] 
TELLEFSEN RELATION OF AGE TO SIZE 
Five cells were selected from each tissue visible in the cross sections of 
about one hundred roots. The cells were chosen at random save those of 
the cortex. These latter were selected from the spherical cells within the 
cortical rays. Measurements were made in the same manner in each case. 
The cells were measured first through their tangential diameter and then 
through their radial diameter. The thickness of the cell walls was measured. 
All measurements were recorded in microns. 
Because of the large amount of aeration tissue present, there was obvious 
difficulty in securing complete longitudinal sections of the roots. However, 
five cells were selected from the epidermis and five from the cortex of each 
of about thirty roots. In each case the first measurement was taken through 
the center of the long axis of the cell; the second measurement was made 
through the center of the short axis of the cell. Data were recorded in the 
same manner as for the cross sections. 
Table i. Measurements in Cross Section of Epidermal Root Cells of Ciitti?igs of Trees of 
Salix nigra Marsh., Group A 
Ave. Measure, 
Number of Tree Diameter of Tree 5 Cells 
(Inches) (Microns) 
76 \ 12.94 X 17.26 
302 ^ 11.28 X 13.61 
306 ^ 13.61 X 14.94 
308 \ 12.60 XI 1.28 
318 11.95 X 10.29 
321 1^ 12.61 X 12.28 
340 —I 9.62 X 10.62 
343 —I 10.29x12.28 
357 -I 11.95 X 12.26 
364 —I 10.62 X 9.29 
401 2 10.29 X 10.28 
606 2 8.96x12.28 
608 2 13.28 X 11.95 
616 2 9.29 X 9.29 
636 ih 13.28x13.94 
637 2 14.44x18.93 
638 2 9.96x13.77 
707 2 10.79x20.25 
710 I 8.95x13.01 
713 I 11.62 x 13.08 
714 10.78x10.95 
715 2 10.78x16.27 
716 I 8.96x13.44 
717 2 12.28 X 13.01 
719 1 1.62x13.94 
720 lh-2 10. 2Q X 13.77 
724 2 11.78 X 14.60 
733 I 12.39x12.28 
734 I 11.62 X 13.61 
735 2 11.95 X 15.27 . 
737 I 9.96x12.82 
746 I 11,22 X 15.27 
Average 11.31 x 13.31 
