ELECTRICITY AND PLANT-GROWING. 59 



deutzias, and chrysanthemums. It was found that this discolora- 

 tion did not extend beyond the first layer of palisade cells. 

 Plants which received solar light by day and electric light at night 

 only, were injured in the same manner but in a less degree. The 

 injury was most marked upon the old leaves. The pelargoniums 

 soon sent out new shoots and the young leaves resisted the action 

 of the light much longer than did the mature ones. The flax 

 continued to grow and the barley ripened. It was found that 

 plants under the electric light alone were able to assimilate, but 

 the action was very slow. As much assimilation took place in an 

 hour on a bright summer day as in several days of electric light. 

 At the expiration of two weeks the condition of the plants was so 

 bad that a change was made, and thereafter a globe was used 

 upon the lamp. Deh^rain also found that while established plants 

 may continue to live and even to grow when exposed only to an 

 electric light, sprouting seeds die before making true leaves. The 

 functional difference between the germinating seed and the inde- 

 pendent plant is expressed by the fact that in the former oxygen 

 is freely absorbed and carbonic acid gas is given off, while in the 

 mature plants the reverse is true in the main — carbonic acid gas is 

 freely taken in and oxygen is freely given off ; but it is not known 

 whether these processes are concerned in the widely different 

 effects which the light exerts upon these stages of vegetation. I 

 have also observed an injury to follow in exposing very young 

 plants to the arc light, but I cannot account for its cause. 

 Deherain's general conclusions in regard to the influence of 

 electric light upon plants are as follows : 



"1. The electric light from lamps contains rays harmful to 

 vegetation. 



2. The greater part of the injurious rays are modified by a 

 transparent glass. 



8. The electric light contains enough rays to maintain full- 

 grown plants two and one-half months. 



4. The light is too weak to enable sprouting seeds to prosper 

 or to bring adult plants to maturity." 



At this point our own experiments were projected. These were 

 begun in January, 1890, and have been continued uninterruptedly 

 during the forcing season to the present time. I shall now invite 

 your attention to a general survey of these investigations, referring 

 you to our three bulletins upon the subject for the details. I 



