I'JO-l.J 



PUBLIC DOC'IIMKNT— No. 



• to 



25 



Tables X. and XI. show oxju'i-iiiK'nts anaiigod .similar (o 

 the two prei'cdiiiu: tables, except that atmo.spheric electricity 

 is substituted for one of (he direct currents. The atmos- 

 pheric ex[)eriments were coiuhicted with some modification 

 from those jjreviouslj' described with radishes. 'I'he })rin- 

 ci})al dillerence, however, consisted in the })ole being 47 

 feet from the ground, instead of 35 feet, and the lunnber of 

 coj)i)er i)oints was 124, instead of 24. (See Fig. 2, No. 3.) 

 In the latter ease we also used a 2H-inch metal bicycle wheel 

 to support the points at the top of tlu^ pole ; in the former 

 arrauiicmeut an inverted umbndla frame was used. In No. 

 2il we endeavored to maintain a current of .2 milliamperes ; 

 Nos. 81 and 33 gave the usual current, but no attempt was 

 made to obtain averages in the latter. A sensitive galva- 

 nometer usually showed a deflection of the needle when in 

 circuit with the atmospheric electrodes ; and when the wire 

 from the pole was attached to a Thomson self-recording 

 electrometer it Avas usually sufficient to deflect the needle 

 and to charge slightly a glass case of 30 cubic feet capacity. 

 Onlv occasional observations were made of the strenirth of 

 the current in experiments shown in Table XI. 



SuMMAKV. — Showing the ItesuU^i wilh Letlucc (Lactuva saiiva L.) given 



in Tables VIII.-XI. 



Treatment. 



Direct current (weiik) ; copper plate electrodes; Nos. 23, 

 26, 29, 32 



Direct current (stronger) ; copper plate electrodes ; Nos. 

 -'4,27, 



Copper and zinc plate electrodes, connected; Nos. 25, 

 28,31,33, 



Atmospheric electricity; copper plate electrodes; Nos. 

 30, .34, . . . ■ 



Number 



of 

 Plants. 



94 

 46 



48 

 47 



Average 

 Current, 



in 



Milliani- 



peres. 



0.184 

 0.367 

 0.214 



Total 



Per Cent. 



gained. 



22.78 

 40.76 

 36.48 

 39.22 



Average per cent, of weight gained, in grams, . 



34.81 



The average percentage of gain shoAvn by lettuce is 

 slightly higher than that given by radishes, although the 

 acceleration is not so great as that shown in the growth of 

 radish tops over roots. There are, however, no instances in 



