1912] BRUSH—MECHANICAL TISSUE 467 
That longitudinal tension may enter into this experiment is 
quite possible; however, in many tendrils in this experiment where 
pressure was applied, the contact with the rubber tubing was so 
close as to permit of a seemingly small amount of longitudinal 
stretching. That this increase was not in the main due to longi- 
tudinal tension may be inferred by a comparison with the results 
in table VII. 
TABLE VII 
PERIOD 28 DAYS 
PRESSURE WITH WEIGHT CONTACT PRESSURE 
Tendril Final wt. Breaking strength Tendril Breaking strength 
H, 15 grams 625 grams Hz 520 grams 
Ky 20 600 
Ka 15 685 K 740 
K, 5 775 
L, 20 540 
L; 20 690 L, 650 
L, 15 875 L; 675 
M; 20 875 
Me 20 600 M: 600 
M, 15 975 
N,; 20 775 
N2 20 035 N; 675 
oe 15 675 
r 20 799° 
S: 15 890 ; Ss 575 
Averages “ 7A5 634 
In order to determine how great a part pressure actually has 
in the formation of mechanical tissue in tendrils, weights were 
placed upon the most sensitive part of the tendril, the latter being 
supported by a small platform suspended from above by a cord. 
Weights were added exactly the same as when tension was used in 
the former experiments, and the same length of the tendril was 
placed under pressure as was calculated to be under pressure in 
the tension experiments. 
The breaking strengths of these tendrils as given in table VII 
. show a slight increase over those tendrils which had contact alone. 
We infer from this that the additional radial pressure caused by an 
amount of tension equal to 20 grams does not greatly increase 
