1004.] 



PlI HLIC DUCUiMKNT — No 





21 



The ct)iK'lu(liii«4- expt'i-iiiuMits with nidishcs aiv shown in 

 tabU's VI. and VII. In this series the atniosphcric experi- 

 ments were omitted, and two direct eurrent experiments 

 were run in each series, in whieli dillerent strengths of cur- 

 rents were employed. In these exi)eriments, and all others 

 which follow, an attempt was made to r(>gulate 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 experiments ; this 

 enabled us to modify resistance, and to maintain a tolerably 

 uniform current throughout. Current records in all the 

 remaining radish exi)erinients are averages for the whole 

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

 minimum and maxinuun 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 ever}- three days, but nt) attempt was made to 

 modity the current strengths, inasnuich as these boxes gen- 

 erally maintained the desired current. 



The results shown in these tables arc more uniform than 

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

 care we o-ave in maintaininjT a more or less uniform stimulus. 

 No loss is shown by the treated ones ; on the other hand, 

 there is considerable acceleration shown by treatment. 



SuM3iARY. — Showing the Results with Radishes (Raphanus sativus L.) 

 given in Tables I., II., IV.-VII. 



Treatment. 



Direct current (weak); copper plate electrodes; 

 No8. 1, 4, 11, 14, 17, 2() 



Dire<'t current (stronger) ; copper plate elec- 

 trodes; Nos. 18, 21, 



Direct curi'ent; wire electrodes; Nos. 2, 5, 



Interrupted induced current; copper plate elec- 

 trodes; Nos. 3, 8. 



Copper and zinc plate electrodes, connected; Nos. 

 7, 13, IK, 19, 22, 



Atmospheric electricity ; copper plate electrodes; 

 Nos. 6, 12, 15 



Number 



of 

 Plants. 



1,334 



.')34 

 360 



334 



1,146 



738 



Per Cent. 



gained in 



Weight of- 



Roots. 



9.73 



14.32 



3.50 



18.87 

 44.49 

 12.67 



Tops. 



39.66 



76.. 51 

 11.18 



8.76 



76.33 



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, 



Of tops, 



Of whole plant, . 



17.26 

 42.95 

 27.34 



