I. Third Report upon Electro-Horticulture. 



For four winters we have made a study of the influence of the elec- 

 tric arc lamp upon plants grown in greenhouses. The results of these 

 investigations, so far as published, appear in Bulletins 30 and 42. 

 During two winters the lamp was hung inside the house, and part of the 

 time the light was naked and at other times screened by a glass globe. 

 It was found that lettuce was greatly hastened in growth by the light, 

 and various flowers were earlier and brighter under its influence. 

 Many plants were injured by the naked light, but sustained no injury 

 or were even benefited by a light which was modified by passing 

 through an opal globe or even through common glass. It therefore 

 seemed reasonable to expect that if the light were placed above the 

 house the glass roof would afford a sufficient screen, and this feature of 

 the investigation was the particular subject of the bulletin last year 

 (Bulletin 42, September, 1892). It was found that radishes and other 

 plants which were injured by a naked light inside the house and even 

 by a light modified by an opal globe, were benefited by a light above 

 the roof; and lettuce and flowers still showed a marked benefit from it. 

 This experiment was repeated last winter and the results are given in 

 the sequel. We also continued our observations upon the effect of 

 colored glass screens interposed between the lamp and the plants for 

 the purpose of ascertaining what part of the spectrum influences 

 plants — an inquiry which we mentioned last year but upon which no 

 report has heretofore been made. Finally, we have to report a prelim- 

 inary investigation to determine to what distance the influence of the 

 light extends. 



Gaulifloroers. 1. The Light above the House. 

 We had already demonstrated to our satisfaction when our last report 

 was made (Bulletin 42) that lettuce is much benefited by electric light 

 passing through a greenhouse roof; and our experiments also showed 

 that flowers may receive a like benefit. In short, no plants which we 

 grew were injured by such light with the single exception of cauli- 

 flowers, which were decidedly poorer in the light house than in the 



