1004.] 



PUBLIC I)( )CUMEiNT — No. 



21 



The concluding experiments with radishes are shown in 

 tables VI. and VII . In this series the atmospheric experi- 

 ments were omitted, and two direct current experiments 

 were run in each series, in which different strengths of cur- 

 rents were employed. In these experiments, and all others 

 which follow, an attempt was made to regulate more care- 

 fully the current strengths, and to make daily readings of 

 the same. For this purpose a water rheostat was introduced 

 in the circuit in the two direct current ex})eriments ; this 

 enabled us to modify resistance, and to maintain a tolerably 

 uniform current throughout. Current records in all the 

 remaining radish experiments are averages for the whole 

 period, and are based on four readings each day. The 

 minimum and maximum currents are given in parentheses. 

 In the direct current series we endeavored to maintain .2 

 and .4 milliamperes respectively. In No. 17, however, it 

 only averaged .1 milliampere ; in Nos. 19 and 22 readings 

 were made every three days, but no attempt was made to 

 modify the current strengths, inasmuch as these boxes gen- 

 erally maintained the desired current. 



The results shown in these tables are more uniform than 

 in the preceding ones, as might be expected from the greater 

 care we gave in maintaining a more or less uniform stimulus. 

 No loss is shown by the treated ones ; on the otht^r hand, 

 there is considerable acceleration shown by treatment. 



Summary. — Shoivimj the L'csnUs wiih Radishes (^Raphanus salivus L.) 

 given in Tables /., //., IV.-VII. 



Treatment. 



Direct current (weak); copper plate electrodes; 

 Nos. 1,4, 11, 14, 17, 20, 



Direct current (stronger) ; copper plate elec- 

 trodes; Nos. 18, 21, 



Direct current; wire electrodes; Nos. 2, 5, 



Interrupted induced current; copper plate elec- 

 trodes; Nos. 3, 8, 



Copper and zinc plate electrodes, connected ; Nos. 

 7, l."}, Ifi, 19, 22 



Atmospheric electricity; copper plate electrodes; 

 Nos. 6, 12, \ft 



Number 



of 

 Plants. 



1,334 



.'>34 

 360 



334 

 1,146 



738 



Per Cent. 



gained in 



Weight of — 



Roots. Tops 



9.73 



14.32 

 3.50 



18.87 



44.49 



12.67 



39.66 



76.. 51 

 11.18 



8.76 



76. ;« 



45.28 



Total 



Per Cent. 



gained. 



23.67 



34.26 

 6.73 



12.40 



.58.56 



28.47 



Average per cent, of weight gained, in grams: — 



Of roots 17.26 



Of tops 42.95 



Of whole plant, 27.34 



