Second Report Upon Electro-Horticulture. 



Beginning with the opening of the year 1890, a series of experi- 

 ments was inaugurated upon some of the relations of electric 

 lighting to plants grown in glass-houses, and the results of the 

 experiments for two winters were published a year ago (Bulletin 

 30). It was found that the electric light profoundly affects many 

 plants, some injuriously and a few beneficially. Lettuce appeared 

 to be greatly assisted by the light, and some ornamental plants 

 produced earlier and brighter flowers under its influence. The 

 experiments were all made with an arc lamp which hung inside 

 the house, and it was found that better results were obtained, 

 when the arc was screened by an opal globe or even by a panes 

 of window glass. The question at once arose if this screen could 

 not be afforded with equal advantage by the glass roof itself 

 if the light were hung above it; and if this were true, it must 

 then be determined how far the beneficial effects of the light 

 would extend, or, in other words, how much glass one light can* 

 cover. It is this particular point which the following paper 

 considers. It may be said, in passing, that several other impor- 

 tant investigations are in progress, but we are not yet ready to 

 report upon them. Perhaps the most important of these investi- 

 gations is one in which the light is passed through colored 

 » screens of known value, in order to determine what parts of the 

 spectrum produce the singular results which we have observed. 



We shall now consider, therefore, what are the effects upon a 

 few common plants of an electric street-lamp suspended above a 

 green-house. The arrangement of the experiment will be under- 

 stood at a glance from the cross-section of the houses under 

 discussion. It will be noticed that there are two 

 parallel houses; each is divided in the middle into two compart- 

 ments. These houses are sixty by twenty feet. In the valley 



