With lettuce it was found that the nearer the plants were to the light the worse the effect; and conversely those furthest away were the best developed.  Cress and endive gave the same results.  In the case of the latter, some of the plants were shaded from the light by an iron post, and these grew better and were larger than those exposed to its direct rays.  The average weight of eight plants in full light was 49.6 grains, as opposed to an average of six plants in the shade of 93.8 grains.  Radishes were strongly attracted to the light and moved toward it during the night.  During the day they straightened up, but moved again toward the light at night.  The plants nearest the lamp made a poor growth and were nearly dead at the end of six weeks.  Averaging the weight of plant, of top and of tuber, it was found that those grown in the dark were heavier in every instance than those grown in the light; and the percentage of marketable tubers from the light-grown plants was twenty-seven, as opposed to seventy-eight in the dark.  Chemical analyses showed the plants in the light to be more mature than those in the dark, although they were much smaller.  Dwarf peas showed the same facts, those in full light being smaller than those in the dark.  The former bloomed a week earlier than the latter, but the production of seed was less, being only about four-sevenths as great.

Further experiments were made by excluding the sun during the day and exposing the plants to the diffused electric light only.  In all cases, with radishes, lettuce, peas, corn, and potatoes, the plants died in about four weeks.  Only a little starch and no chlorophyl was found in the plants deprived of sunlight and only receiving the electric light.  Thus the experiments with a naked light showed conclusively that “within range of an ordinary forcing house the naked arc light running continuously through the night is injurious to some plants.”  In no case did it prove profitable.

Experiments with the light inclosed in a white globe and running all night were different in their results.  The effect was much less marked.  Lettuce was decidedly better in the light house; radishes were thrifty but did not produce as much as in the dark house.  A third series of experiments with the naked light running a part of the night only were also made.  Radishes, peas, lettuce, and many flowers were experimented upon.  The lettuce was greatly benefited by the light.  “Three weeks after transplanting (Feb. 5),” we are told, “both varieties in the lighthouse were fully 50 per cent. in advance of those in the dark house in size, and the color and other characters of the plants were fully as good.  The plants had received at this time 701/2 hours of electric light.  Just a month later the first heads were sold from the light house, but it was six weeks later when the first heads were sold from the dark house.  In other words, the electric light plants were two weeks ahead of the others.  This gain had been purchased by 1613/4 hours of electric light, worth at current prices of street lighting about $7.”