Transpiration and the Resistance of Stems 



341 



Abut Hon 5 7 



56 



57 



57 



56.5 

 57 



c 



55 

 55 

 54 



54 



54-5 



54 



60 

 60 

 60 

 61 

 61 

 62 



C 



57 

 57 

 56 

 56 

 56 



55 



63 

 62 



61 



61.5 



62 



62 



c 



59-5 

 60 



58 



59 



58.5 

 59 



1 40 

 X 50 

 2 20 

 2 22 

 225 

 2 26 



c 



2 29 

 30 



228 



2 27 



2 26 

 26 



234 

 2 S1 

 2 29 



2»2 

 2 35 



2 36 



c. 



2 31 

 30 

 2 29 

 2 29 



230 

 2 30 



The columns marked C give the rate with the current on, RC with the current re- 

 versed, those unmarked without the current. 



The results as far as showing any effect upon the conductivity 

 of the xylem is negative. The current from the static machine 

 and also weak dynamic currents had no effect. 



The variations in the above examples which are taken from ex- 

 periments with street current are due to the high resistance of 

 the stem to the current. This resulted in a rise of temperature 

 and the change of rate. The records of temperature in the pre- 

 ceding work have not been given inasmuch as the examples 

 selected for illustration have not been subjected to any variations 

 in this respect that are of importance. In the test upon Abutilon, 

 for the purpose of producing variations in the conductivity of the 

 stem, a ifo NaCl and an isotonic cane-sugar solution were used in 

 place of water, the measurements with the latter occurring in the 

 four right-hand columns. The results are the same as with water. 



Salt Solutions and Rate 



The marked influence of salt and sugar upon the rate in the 

 last experiment led to some further tests for the purpose of de- 

 termining if there was any specific peculiarity in the cell wall that 

 might be revealed by the rate of transmission. Solutions of ZnCI 2 

 and sugar were prepared isotonic with a decinormal solution of 

 NaCl and stems were subjected to these different solutions under 

 constant pressure. 



IV. 



Tax us 



H a O 



2 34 

 2 34 

 2 34 



NaCl 

 2 20 



221 

 232 



H 2 



2** 



25 

 2 32 



ZnCl t 



2 IS 



H a O NaCl H a O ZnCi, 



Acalypha 



2 



21 



31 



2 35 



235 



2 34 



2 40 



2 35 



2 3« 



2 35 



2 34 



2 35 



234 



2 40 



236 



I>» 



,18 



I" 

 X 19 



H8 



52 



5 2 



5i 



50 



49 

 49 



64 

 69 



70 



72 



74 

 78 



61 



59 



59 

 62 



63 



