ELECTRICITY AND PLANT-GROWING. 57 



plants, although experiments made by one of my foi-mer pupils, 

 and yet unpublished, show that it may hasten growth. But the 

 amount of light is much less than in the arc-lamp, as the ordinary 

 incandescent bulbs give from sixteen to fifty candle-power only. 

 But we hope to investigate the subject soon. 



If the electric light, therefore, is similar to sunlight in essential 

 effects upon plants, it remains for us to discover two things : 

 1. Does the light contain injurious properties along with illumin- 

 ation? 2. Are all plants equall}' susceptible to its influence? 



Although Herve-Mangon had demonstrated in 1861 that the 

 electric light can occasion the production of chlorophyll or green 

 matter in plants, and that it can produce heliotropism or draw 

 plants towards itself, and although Prillieux had shown in 1869 

 that it is capable of promoting assimilation, it was not until near 

 the close of the seventies that any application of the light to 

 horticultural purposes was attempted. The first horticultural 

 experiment was made in England by Dr. C. W. Siemens, a 

 renowned physicist. Siemens experimented with a variety of 

 forced plants, mostly those which produced edible fruits, as straw- 

 berries, tomatoes, grapes, and melons. Upon all these plants the 

 effect of the arc light was marked, sometimes injuriously and 

 sometimes beneficially. Dr. Siemens soon found that a naked or 

 unscreened light was injurious to plants at short range, but that 

 the interposition of a clear glass globe or an ordinary window 

 pane prevented such injury. He demonstrated that the light can 

 be placed aliove the house with good results, and thereby also 

 showed that the modification of the plants was due to illumination 

 and not to electrification nor to products of combustion. In 

 general, plants were earlier under the screened light than in 

 natural conditions ; that is, thej' grew more rapidly, and this is 

 the result which we should have anticipated, if it is true that the 

 electric light simply lengthens the day. At the close of his 

 experiments, Siemens was very sanguine that the electric light can 

 be profitably employed in horticulture, and he used the term 

 "electro horticulture" to designate this new application of electric 

 energy. He anticipated that in the future " the horticulturist will 

 have the means of making himself practically independent of solar 

 light for producing a high quality of fruit at all seasons of the 

 year." He had shown that growth can be hastened by the addi- 

 tion of electric light to daylight, that injury does not necessarily 



