1904.] 



PUBLIC DOCUMENT — No. 33. 



35 



of the case and focu.scd upon the apex of the plant, measure- 

 ments being taken every fifteen miiuites. 



The following figure shows the results of one experiment. 

 A small tomato plant about four inches high was placed in 

 the case, and treated as before described. Measurements of 



I 2 



Fig. 1. — Growth curve of tomato plant. The horizontal divisions represent periods 

 of fifteen minutes in time; the vertical divisions represent degrees of temperature, 

 also humidity, electrical potential and increments of growth. T, temperature; H, 

 humidity; P, electrical potential; G, growth. 



gi'owth were recorded every fifteen minutes, from 10.15 a.m. 

 to 5 P.M. From 10.15 until 11.30 there Avas no perceptible 

 growth. At 10.30 the air in which the plant was growing 

 was charged to a potential of 70 volts. Half an hour later, 

 at 12 o'clock, the plant had grown two spaces on the microm- 

 eter scale; and at 12.15 had grown two more spaces; and 

 so on until 2.15, when no growth was recorded. At 2.45 

 the air in the case was recharged to 80 volts, and a greatly 

 increased growth resulted, the maximum acceleration taking 

 place at 1.15 and 4 o'clock respectively, as a result of the two 

 stimuli. 



This is but one of many similar figures showing the results 

 of our experiments, tomato plants, corn cotyledons and bread 

 moulds {tnucor and Pliycomyces nitens) being used. In all 



