Gregory : Effects of pressure on roots of Vicia Faba 459 



fill the crack. The blocks were kept with the bands upon them. 

 To estimate the amount of pressure : the number of cardboard 

 strips that had been determined before was placed between the 

 blocks ; the upper block was then fastened in a clamp on a 

 standard and a weighing pan attached to the lower block ; weights 

 were then applied until the blocks were stretched apart enough to 

 allow the cardboard strips to slip out. 



Table of Measurements. 



No. of experiment. 



Time of 



Length of root 



Uhickness of root 



Total ainouut of 



A 



compression. 



after pressure. 



after pressure 



pressure 



1 



I 



1 



24 hours. 



14 mm. 



.66 mm. 



858 gm. 



II 



1 1 



8 '« 



1.045 " 



860 " 



III 



i i 



9 " 



.38 " 



1559 " 



IV 



t( 



12 " 



•45 " 



1650 " 



V 



1 



ei 



12 " 



■75 " 



1902 " 



VI 



(C 



II " 



•74 " 



1553 " 



VII 



1 



13 " 



.605 " 



1103 " 



VIII 



ti 



7 " 



•735 " 



958 " 



IX 



C( 



6 " 



1.020 " 



958 " 



X 



i I 



5 " 



1.035 " 



1759 " 



XI 



it 



7 " 



•775 " 



1759 " 



XIT 



12 hours. 



8 " 



.828 " 



1359 " 



XIII 



4i 



8 " 



.750 " 



2050 '♦ 



XIV . 



ti 



7 " 



1. 615 " 



1253 " 



XV 



it 



7 " 



.80S " 



662 " 



XVI 



10 hours. 



10 " 



.500 " 



1625 " 



XVII 



it 



10 " 



1.025 " 



1625 " 



Very little of importance can be deduced from the thickness of 

 the compressed roots since a measurement was not taken before 

 the pressure was applied. As a result there are many cases giv- 

 ing seemingly contradicting results. For example, in experiment 

 IX, after a pressure of pjS grams, the root measured 1.02 mm. 

 in thickness ; in experiment X, however, after a pressure of //S9 

 grams, the root measured 1.03 in thickness. This could probably 

 be explained if the measurements of the roots before pressure were 

 known. In the first seven experiments the roots used were of 

 approximately equal size. Here the average thickness of roots 

 affected by the minimum amount of pressure is .85 mm.; by the 

 maximum amount of pressure, .58. In either case the normal 

 root has been greatly compressed. 



An examination of the material shows that contrary to the 

 view of Kny and to the results of Pfluger and of Driesch, pressure 



