239 



light -was mndifiefl by a rloar mlnss fjlol.r. In tlic ))it sppds ;m(1 plants of lunHtard, 

 (■allots, liiiiiips, licaiiM, (iiicimilitiis, and nudons wen- placed. JLc Jiglil ran ti Iiouih 

 each night and the jdaiils had sniilijilit <lniinji; the day. In all cases those jilants 

 "('XI)os(hI to hotli sources of light showed a decided supeiioiity in vigor over all the 

 others, and the green of the leaf was of a dark, rich hue." Heliotroiiism was 

 ohserved in tln^ young mustard plants. Electric light apj)eared to he about half as 

 elVectivc as daylight. A great difficulty experienced in this experiment wasthelilm 

 of moisture which condenses on greenhouse roofs at night and obstructs the passage 

 of light. The light was at one time suspended over two parallel )»its nearly 4 feet 

 apart, and the effect was observed upon plants under the glass and in the uncovered 

 space. In all cases the growth of the plants was hastened. Flowering was hastened 

 in melons and other plants under the glass. Strawberries which were just setting 

 fruit were jtut in one of the pits antl part of them were ke^^t dark at night while 

 others were exposed to the light. After 14 days, the light having burned 12 nights, 

 most of the fruits on the lighted plants "had attained to ripeness, and presented a 

 rich coloring, while the fruit on those plants that had been exposed to daylight only 

 had by this time scarcely begun to show even a sign of redness." He concludes that 

 a lani}) of 1,400 caudle power produced a maximum beneficial result on vegetation 

 at a distance 3 meters (nearly 10 feet) above the glass, but " the effect is nevertheless 

 very marked upon plants at a greater distance." 



At the|close of his experiments Siemens was very sanguine that the electric light can 

 l)e profitably employed in horticulture, and he used the term "electro-horticulture" 

 to designate this ncAV application of electric energy. * * * 



Deh<Srain's exj)erimeuts * were conducted at the Exposition d'Electricit^, Paris 

 in 1881. A small conservatory standing inside the Exposition building was divided 

 into two compartments. One compartment was darkened and the glass painted 

 white ujjon the inside; this received the electric light and all solar light was 

 excluded. The other compartmeut was not changed. * * * 



A lamp of 2,000 nominal candle power was used. At first the naked electric liohl 

 was used and it ran continuously. 



[A number of different kinds of plants were experimented with.] At the expira- 

 tion of 2 weeks the condition of the plants was so Ijad that a change was made and 

 thereafter a transparent glass globe was used upon the lamj). 



[From his exiieriments Deh<5rain drew the following conclusions :] 



(1) The electric light from lamps contains rays harmful to vegetation. 



(2) The greater part of the injurious rays are modified by a transparent Wass. 



(3) The electric light contains enough rays to n\aiutain full-grown plants 2^ 

 months. 



(4) The light is too weak to enable sprouting seeds to prosjier or to brino- admt 

 plants to maturity. 



Finally, observationst were made more recently upon the influence of the electric 

 light upon plants in the Winter Palace at St. Petersburg. It was observed that in a 

 single night ornamental plants turned yellow and then lost their leaves. Yet it is 

 well known that incandescent lamps can be lodged in the corolla of a flower without 

 injuring it. 



Recapitulation. — The aiitlior does not consider tliat the results thns 

 far obtained will warrant many definite conclusions. 



Yet there are a few points which are clear: The electric light pi-omotes assimila- 

 tion, it often hastens growtli and maturity, it is capable of producing natural flavors 

 and colors in fruit, it often intensifies colors of flowers, and sometimes increases the 

 production of flowers. The experiments show that periods of darkness are not 

 necessary to the growth and development of plants. There is every reason, there- 

 fore, to siippose that the electric light can be profitably used in the growing of plants. 



•Ann. Agron., 7, 551 (1881). t Ann. Agron., 14, 281 (1888). 



