34 
THE FLORIST AND POMOLOGIST. 
[ April, 
Dahlias really are. We have no doubt other 
choice forms will in due time appear, for in 
our limited experience we have had other 
seedlings, which indicate still greater variety. 
Amongst them were two liliputians, one 
yellow, the other scarlet, with flower-heads 
just the size for button-hole stars, and which, 
if they keep true, will be invaluable for the 
louquetiers. One had yellow florets, tipped 
with red ; another, scarlet florets, with a ring of 
yellow around the disk; a third had yellow 
florets, streaked or flushed with fiery-orange; 
and a fourth had scarlet florets, with golden 
tips. The development of these during the 
next season will be a source of much interest. 
One prominent feature in all the Dahlias of 
this type is that the flower-heads are supported 
by long and slender stalks, which greatly facili¬ 
tates their effective employment as cut flowers. 
T. Moore, Chelsea. 
ELECTRO-ILLUMINATION FOR 
GAEDENS. 
CppT has for some time been known that 
& K Siemens was engaged in making 
GA) experiments with the view to ascertain 
whether or not electric light exercised any 
visible effect on the growth of plants. So far 
as they have gone, these experiments supply to 
this question a distinctly affirmative reply. At 
the meeting of the Royal Society on March 
4, Dr. Siemens gave an account of his pro¬ 
ceedings and their results, and from a summary 
of his paper published in the Gardeners 
Chronicle , we glean the following particulars :— 
The experiments were made by means of a 
lamp of 1,400 candle power, provided with a 
metallic reflector, and placed in the open air, 
about 2 metres (nearly 7 feet) above the glass 
of a sunk melon-house, in which a number of 
quick-growing plants in pots, such as mustard, 
carrots, swedes, beans, cucumbers, and melons, 
were placed. It was thus possible to bring the 
plants at suitable intervals under the influence 
of day-light and electric-light without moving 
them, the light in both cases falling upon them 
at the same angle approximately. The pots 
were divided into four groups, of which one 
was kept entirely in the dark, one was ex¬ 
posed to the influence of electric light only, 
one was exposed to the influence of daylight 
only, and one was successively exposed to 
both daylight and electric light. The electric 
light was supplied for six hours each even¬ 
ing, from 5 p.m. to 11 p.m., all the plants 
being left in darkness for the remainder 
of the night. In all cases, the differences of 
effect were unmistakable. The plants kept in 
the dark were pale yellow, thin in the stalk, 
and soon died. Those exposed to electric light 
only showed a light-green leaf, and had suffi¬ 
cient vigour to survive. Those exposed to day¬ 
light only were of a darker green and greater 
vigour. Those exposed to both sources of light 
showed a decided superiority in vigour over all 
the others, and the green of the leaf was of a 
dark rich hue. The time of exposure was 
indeed in favour of solar light in the propor¬ 
tion of nearly two to one, but all allowance 
being made, daylight appeared to be about twice 
as effective as the electric light. The latter, 
however, was not well placed for giving out its 
power advantageously. The nights being cold, 
and the plants under experiment for the most 
part of a character to require a hot moist 
atmosphere, the glass was thickly covered with 
moisture, which greatly obstructed the action 
of the light; besides which, the electric light 
had to pass through the glass of its own lamp. 
Notwithstanding these drawbacks, electric light 
was found to be sufficiently powerful to form 
chlorophyll and its derivatives in the plants. 
These preliminary trials seemed to prove that 
electric light can be utilised in aid of solar 
light by placing it over greenhouses, though 
the loss of effect must there be considerable. 
The effect of the light upon plants, when both 
were placed in the same apartment, was there¬ 
fore made a subject of enquiry, and under 
these conditions it was found that the plants 
which had the double benefit of day and 
electric light, far surpassed the others in depth 
of green and in vigorous appearance generally. It 
was, moreover, ascertained that the carbonic and 
nitrogenous compounds produced within the 
electric arc did not exercise any deleterious 
action upon the plants; and it vvas further 
found that the electric light, when put into 
conservatories or greenhouses, does not injure 
the plants, but rather improves their appear¬ 
ance and growth, the leaves assuming a darker 
and more vigorous appearance, and the colour¬ 
ing of the flowers becoming more vivid. 
These experiments are not only instructive 
as proving the sufficiency of electric light alone 
to promote vegetation, but they also indi¬ 
cate the important fact that diurnal repose is 
not necessary for the life of plants, although 
the duration of the experiments is too limited, 
perhaps, to furnish the proof in an absolute 
manner. It may, however, be argued from 
analogy that such repose is not necessary, see¬ 
ing that (annual) crops grow and ripen in a 
wonderfully short space of time in the northern 
regions of Sweden and Norway and Finland- 
