1912] BRUSH—MECHANICAL TISSUE 459 
was used for killing and fixing material, as this preparation pene- 
trates woody tissues very rapidly. Sections were stained in 
TABLE I 
DURATION OF EXPERIMENT 32 DAYS; FINAL WEIGHT USED 20 GRAMS 
With support With ligature 
POs veel te ly Ios50 grams 1200 grams 
§ 97 
Bi 5 aia. pa a aatiaiee ie 1050 ) 1265 
ere ree Ese Un 1275 1475 
Ae Oe ee aes 1350 1250 
Bek sic ees wave oie 1425 lee 
775 
GO ing eee 750 1 025 
1 Ra Gae pee aero AND Hts 820 925 
Average 55.08% 1103 grams 1140.5 grams 
anilin safranin in order to bring out clearly the lignified tissues. 
Permanent slides were made by mounting in Canada balsam. 
Further detailed methods are given in each experiment. 
Experimental work 
DETAILS OF EXPERIMENTS 
1. Tendril free, with contact, with contact and tension.—In the 
first series of experiments, tendrils were placed under the following 
three conditions: (1) without any contact whatever, (2) with 
contact alone, and (3) with contact and tension. In the last case, 
contact was secured by allowing the tendril to twine about a 
support as before described. The three tendrils of each set to be 
compared were chosen from the same vine according to the methods 
previously given. A final weight of 20 grams was chosen after a 
few preliminary trials, which showed that 20 grams was the highest 
weight which could be used on the average Passiflora tendril with- 
out producing a weakening effect. The breaking strength of 
these tendrils is given in table II. 
These results show clearly an increase in breaking strength due 
to contact, and a still greater increase when tension is applied. 
We have yet to determine, however, whether this increase with 
tension is due to the longitudinal pull or to increased contact, 
