BOTANICAL GAZETTE. 5j 



from either when desired. The pots were divided into four groups: 



1. One pot of each kept entirely in the dark. 



2. One was exposed to the electric light only. 



3. One was exposed to daylight only 



4. One was exposed successively to day and electric light. 



The electric light was supplied from 5 to 11, p. m., the plants being 

 left in darkness the remainder of the night. The result shows what 

 was to be expected in the first group. The second had pale, green 

 leaves, but with sufficient vigor to. survive. The third showed the 

 usual healthy color, while the last were unmistakably superior to all 

 the rest, both in the deeper green of the leaves and greater vigor. 

 In these experiments the time of supplying the electric light was only 

 about half the time of daylight. In the next series the plants were 

 divided into three classes : 



1. Exposed to daylight alone. 



2. Exposed to electric light 11 hours, and kept dark in day. 



3. Exposed to II hours of electric light and 11 hours daylight, 

 (i) had the usual healthy appearance at the end of four days and 

 nights ; (2) were usually lighter in color but in one case darker ; (3) 

 again were plainly superior, more so than before. 



The lamp was next put into a palm house 8 62 m. by 14.42 m. by 4.42 

 m. All the plants therein flourished, but those nearest the light most. 

 No harmful effects from lack of ventilation of the compounds gener- 

 ated by the burning. The conclusions deduced from these experi- 

 ments are as follows : 



1. That the electric light is efficacious in producing chlorophyll 

 and promoting growth. 



2. That an electric center of light equal to 1,400 candles, placed 

 at a distance of 2 meters from growing plants appeared to be equal in 

 effect to average daylight at this season of the year. 



3. That the carbonic acid and nitrogenous compounds generated 

 in diminutive quantities in the electric arc, produce no sensible 

 deleterious effects upon plants inclosed m the same space. 



4. That plants do not require a period of rest during the 24 hours 

 of the day, but make increased and vigorous progress if subjected 

 during daytime to sunlight and during the night to the electric light. 



5. That the radiation of heat from powerful electric arcs can be 

 made available to counteract the effect of night frosts. 



6. That while under the influence of electric light plants can bear in- 

 creased stove-heat without collapsing, which is favorable to forcing by 

 the electric light. 



7. That the expense of electro-horticulture depends on the cost of 

 mechanical energy, but can be made moderate where natural forces 

 can be made available. 



Dr. Siemens' experiments still continue and we shall await the 

 results of longer trials with considerable curiosity. His deductions 

 confirm those of Dr. Schuebeler on the efl"ect of uninterruptedsunlight 

 of the Arctic regions. — C. R B. 



