1004.] 



PUBLIC DOCUMENT— No. 33. 



23 



for their full devolopincnt. In triinsplaiitiiig, however, there 

 was little or no loam attached to their roots. We have 

 handled lettuce so extensively' in our greenhouse that we 

 were familiar with its eharaoteristie re(|uirements, and usually 

 had on hand an ample sup})lj of material from which to 

 select. The strengths of currents in all lettuce experiments 

 where gravity cells were used are based on four daily records. 

 The minimum and maximum currents are also given in paren- 

 theses in all cases. In the cop})er and zinc electrode con- 

 nections the currents were recorded every three days and 

 the tables show the averages obtained. 



Table VIII. — Showing the Effect of Current Electricity upon the 

 Growth of Lettuce (Laciucd ^atica L.). Normal I'lant taken as 

 the atandanl at 100. 



[Duration of experiment, 31 days.] 



No. 



Treatment. 



Number 



of 

 Plants. 



Current, 



in 



Mllliam- 



peres. 



Per Cent, 

 gained 



in 

 Weight. 



23 



24 



26 



Normal, 



Direct current ; copper plate elec- 

 trodes 



Direct current ; copper plate elec- 

 trodes, . . . . ■ . 



Copper and zinc plate electrodes, . 



.54.22 

 60.62 

 47.53 



Total average weight, in grams : — 



Normal, 34.69 



Treated 53.50 



Total per cent, gained 54.22 



Table IX. — Showing the Effect of Current Electricity ux)on the Growth 

 of Lettuce (Lactuca sativa L.). Normal Plants taken as the Stand- 

 ard at 100. 



[Duration of experiment, 42 days.] 



No. 



Treatment. 



Per Cent, 

 gained 



in 

 Weight. 



2<; 



27 

 28 



Normal, 



Direct current 



Direct current 



Copper and zinc plate electrodes, 

 connected, 



21.19 



20.91 



7.39 



Total average weight. In grams: — 



Normal, 28.12 



Treated, 32.73 



Total per cent- gained, t . t » t » > . . i 16-30 



