EXPERIMENT STATION BULLETINS. 585 



tificate and was graduated to tenths of a degree. The thermometer in 

 the conductivity cup was graduated to tenths of a degree, but its accu' 

 racy is unknown. Since only relative changes are to be shown here ex-' 

 treme accuracy in temperature is not necessary. When the temperature >; 

 of the bath was 18° C, that of the cup was 18.2° C. making a variation ' 

 of .2 of a degree. The apparatus was first adjusted with the resistance 

 in the bridge circuit and after a balance had been obtained the current 

 was increased by a removal of the resistance. Immediately the scale 

 deflected in one direction and gradually continued in the same direction. 

 When the deflection reached the end of the scale the current was cut off 

 and the time taken by a stop watch and the rise in temperature of the 

 electrolyte noted. As an average of five tests the end of the scale was 

 reached in 52 seconds and the temperature in that time had risen .8°. It 

 may be mentioned here that when a resistance of 1,000 ohms was in the 

 bridge circuit and the key down two minutes there was no deflection or 

 "creeping" showing that the heating had been effectively eliminated. 



The next two experiments are added in order to show the applicability 

 of the conductivity apparatus described in the present paper to biological 

 problems. As before, the intention is not to list a great number of ex- 

 periments nor explain any in great detail. The method devised in this 

 paper is adaptable to precise and delicate measurement of various biologi- 

 cal phenomena. 



'i 



Experiment V. 



True (38) has shown that the resistance of distilled water decreases 

 when seedlings of lupines or peas are grown in it, and attributes the 

 fall of resistance to the excretion of electrolytes from the roots. His 

 experiments touching on this point were repeated and confirmed. 



Distilled water was used as a culture solution. This was put into >. 

 thoroughly cleaned Jena glass beakers o| 250 cc. capacity. The quantity 

 of distilled water used in the beaker was 200 cc. Seedlings of Lupinus 

 albus were used as indicators. The seeds were first soaked in the same 

 water for about lO hours, then adjusted on parafiined wire hooks which 

 were hung from the edges of the beaker. The seeds were so adjusted that 

 the hypocotyl would, on growing, reach the water in a vertical position. 

 The beaker was covered with a glass plate so that moist conditions could 

 be maintained. When the roots had reached the length of about 2 cm. 

 the experiment was started. The seedlings while on the hooks were re- 

 moved from this improvised germinator, washed thoroughly in fresh con- 

 ductivity water and then suspended in the culture dishes. At the same 

 time the electrodes were plunged into the solution and a reading made. 



At 3 P. M. 3/13/15 the resistance was 29,595 ohms. 

 At 9:30 P. M. 3/13/15 the resistance was 24,945 ohms. 

 At 9 A. M. 3/14/15 the resistance was 19,393 ohms. 

 At 7:30 P. M. 3/14/15 the resistance was 16,125 ohms. 

 At 8:40 A. M. 3/15/15 the resistance was 15,210 ohms. 

 At 3 :30 P. M. 3/15/15 the resistance was 13,735 ohms. 



This experiment shows that the excretion of electrolytes was more rapid 

 and in larger quantities at the beginning than at the end of the given 



