er the light.

It is doubtful whether the incandescent light can be used in
the greenhouse from a practical and economic standpoint on
other plants than lettuce and perhaps flowering plants; and at
present prices (1894) it is a question if it will pay to employ
it even for these.

There are many points about the incandescent electric light
that appear to make it preferable to the arc light for
greenhouse use.

Although we have not yet thoroughly established the economy and
practicability of the electric light upon plant growth, still I
am convinced that there is a future in it.

These are encouraging conclusions, considering the fact that the cost of
light from incandescent lamps at the present time is only a small
fraction of its cost at that time.

In an experiment conducted in England in 1913 mercury glass-tube arcs
were used in one part of a hothouse and the other part was reserved for
a control test. The same kind of seeds were planted in the two parts of
the hothouse and all conditions were maintained the same, excepting that
a mercury-vapor lamp was operated a few hours in the evening in one of
them. Miss Dudgeon, who conducted the test, was enthusiastic over the
results obtained. Ordinary vegetable seeds and grains germinated in
eight to thirteen days in the hothouse in which the artificial light was
used to lengthen the day. In the other, germination took place in from
twelve to fifty-seven days. In all cases at least several days were
saved in germination and in some cases several weeks. Flowers also
increased in foliage, and a 25 per cent. increase in the crop of
strawberries was noted. Seedlings produced under the forcing by
artificial light needed virtually no hardening before being planted in
the open. Professor Priestley of Bristol University said of this work:

The light seems to have been extraordinarily efficacious,
producing accelerated germination, increased growth, greater
depth of color, and more important still, no signs of lanky,
unnatural extension of plant usually associated with forcing.
Rather the plants exposed to the radiation seem to have grown
if anything more sturdy than the control plants. A structural
examination of the experimental and control plants carried out
by means of the microscope fully confirmed Miss Dudgeon's
statements both as to depth of color and greater sturdiness o