ive the general conclusions.
The effect of the naked light running all night was to hasten
maturity, the nearer the plants being to the light the greater being
the acceleration. The lettuce, spinach, etc., "ran to seed" in the
"light" house long before similar plants in the dark. An examination
of the spinach leaves with the microscope showed the same amount of
starch in each, but in the electric light plants the grains were
larger, had more distinct markings and gave a deeper color with
iodine.
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 prof
|